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MEDICAL 


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MANUAL 


OF 


CHEMISTRY 


A  GUIDE  TO  LECTURES  AND  LABORATORY  WORK  FOR  BEGINNERS 

IN  CHEMISTRY.     A  TEXT-BOOK  SPECIALLY  ADAPTED  FOR 

STUDENTS  OF  MEDICINE,  PHARMACY,  AND 

DENTISTRY. 


BY 

w.  SIMO:NT,  PH.D.,  M.D., 

PROFESSOR  OF  CHEMISTRY  IN  THE  COLLEGE  OF  PHYSICIANS  AND  SURGEONS  OF  BALTIMORE, 

IN  THE  MARYLAND  COLLEGE  OF  PHARMACY,  AND  IN  THE 

BALTIMORE  COLLEGE  OF  DENTAL  SURGERY. 


FIFTH   EDITION,  THOROUGHLY   REVISED. 
WITH  FORTY-FOUR  ILLUSTRATIONS 


EIGHT  COLORED   PLATES,   REPRESENTING  SIXTY-FOUR  CHEMICAL 

REACTIONS. 


PHILADELPHIA: 

LEA    BROTHERS    &    CO. 

1895. 


* 


Entered  according  to  Act  of  Congress,  in  the  year  1895,  by 

LEA    BROTHERS    &    CO., 
In  the  Office  of  the  Librarian  of  Congress  at  Washington,  D.  G, 

All  rights  reserved. 


PREFACE  TO  THE  FIFTH  EDITION. 


THE  steadily  increasing  demand  for  this  Manual  has  stimulated  the 
author  to  prepare  this  new  edition  with  great  care  and  with  due  con- 
sideration of  the  needs  of  the  student.  The  many  changes  and  additions 
made  were  necessitated  not  only  by  the  general  advance  of  science,  but 
also  because  of  the  desire  of  the  author  to  bring  this  work  in  complete 
harmony  with  the  new  Pharmacopoeia. 

The  orthography  recommended  by  the  chemical  section  of  the  American 
Association  for  the  Advancement  of  Science  has  not  been  fully  adopted, 
for  the  reasons  that  neither  the  leading  chemical  journals  nor  the  United 
States  Pharmacopeia  use  this  spelling,  and  that  it  would  be  unwise  to 
have  the  student  confronted  with  two  different  systems  of  orthography. 

As  heretofore,  the  subject  has  been  divided  into  seven  parts  each  one 
of  which  contains  so  much  of  the  matter  under  consideration  as  is  believed 
to  be  necessary  for  a  fair  understanding  of  the  subject.  At  the  same  time 
care  has  been  taken  to  place  in  the  foreground  all  facts  and  data  which 
are  of  direct  interest  to  the  physician,  pharmacist,  and  dentist,  and  to 
exclude,  as  far  as  is  compatible  with  the  presentation  of  a  comprehen- 
sive view  of  chemistry,  those  portions  which  are  of  restricted  interest  only. 

In  the  first  part  the  fundamental  properties  of  matter  are  considered 
briefly,  and  to  such  an  extent  as  is  necessary  for  an  understanding  of 
chemical  phenomena. 

The  second  part  treats  of  those  principles  of  chemistry  which  are  the 
foundation  of  the  science,  and  enters  briefly  into  a  discussion  of  theoretical 
views  regarding  the  atomic  constitution  of  matter.  Though  the  author 
prefers  to  present  these  theories  to  his  classes  at  the  proper  times  during 
the  course  of  lectures,  he  does  not  deem  it  desirable  to  have  them  scat- 
tered throughout  the  work,  believing  it  better  to  assemble  them  compactly 
in  print,  so  that  the  student  may  be  able  to  .study  them  after  having 
acquired  some  knowledge  of  chemical  phenomena. 

The  third  and  fourth  parts  are  devoted  to  the  consideration  of  the  non- 
metallic  and  metallic  elements  and  their  compounds.  While  the  periodic 
la\v  furnishes  a  most  admirable  basis  for  a  scientific  classification  of  ele- 
ments, yet  their  consideration  according  to  a  strict  adherence  to  periodicity 
does  not  seem  advisable  in  this  book.  For  this  reason  the  old  classifica- 
tion of  metals  and  non-metals,  organic  and  inorganic  compounds,  has  been 
retained,  since  experience  has  shown  it  to  be  well  adapted  to  the  instruc- 

J3373 


iv  PREFACE  TO  THE  FIFTH  EDITION. 

tion  of  beginners  in  chemistry.  All  our  classifications  of  either  natural 
objects  or  phenomena  are  imperfect,  because  Nature  does  not  draw  those 
distinct  lines  of  demarcation  which  we  adopt  as  necessary  for  our  studies. 
The  most  simple  and  natural  classification  is  therefore  always  to  be  pre- 
ferred, even  if,  as  in  the  above  case,  the  student  might  derive  from  it  the 
impression  that  matter  was  thus  separated  into  distinct  groups. 

Of  elements,  those  only  are  considered  which  have  either  intrinsically 
or  in  combination  a  practical  interest,  or  which  take  an  active  part  in  the 
various  chemical  changes  in  nature. 

For  the  special  benefit  of  pharmaceutical  and  medical  students  all 
chemicals  mentioned  in  the  last  revision  of  the  United  States  Pharma- 
copoeia are  included,  and  when  of  sufficient  interest  they  are  fully 
considered. 

The  fifth  part  is  devoted  to  analytical  Chemistry  and  will  serve  the 
student  as  a  guide  in  his  laboratory  work.  Qualitative  methods  are 
chiefly  considered,  but  a  chapter  is  added  giving  all  official  methods  for 
volumetric  determinations. 

The  sixth  part  treats  of  organic  chemistry.  Though  it  is  impossible  to 
include  within  the  limits  of  this  text-book  an  extended  consideration  of  a 
branch  of  chemical  science  so  highly  developed,  yet  it  is  believed  that  an 
intelligent  study  of  this  part  will  familiarize  the  student  with  carbon 
compounds  sufficiently  to  give  him  a  clear  understanding  of  their  general 
character,  and  a  knowledge  of  the  bodies  which  are  most  important  in 
medical  science. 

The  seventh  and  last  part,  giving  some  of  the  principal  facts  of  physio- 
logical chemistry,  was  prepared  for  the  benefit  of  the  medical  student  in 
particular.  Much  new  matter  has  again  been  added  to  these  chapters, 
and  special  care  has  been  taken  to  mention  the  most  modern  methods  f  jr 
chemical  examination  in  clinical  diagnosis. 

As  an  aid  to  laboratory  work  a  number  of  experiments  have  been 
added  which  may  readily  be  performed  by  students  with  a  comparatively 
small  outfit  of  chemical  apparatus. 

The  decimal  system  has  been  strictly  adhered  to  in  ail  weights  and 
measures ;  degrees  of  temperature  are  expressed  in  the  same  system,  the 
corresponding  degrees  of  Fahrenheit  being  also  mentioned. 

Many  changes  have  been  made  on  the  plates  showing  the  variously 
shaded  colors  of  a  number  of  substances  and  the  nature  of  their  reactions. 
There  has  also  been  added  a  new  plate  illustrating  the  chemical  behavior 
of  a  number  of  the  more  important  benzene  derivatives. 

W.  8. 

BALTIMORE,  January,  1895. 


CONTENTS. 


i. 

FUNDAMENTAL  PROPERTIES  OF   MATTER.    RESULTS  OF  THE 
ATTRACTIONS  BETWEEN  MASSES,  SURFACES,  AND  MOLECULES. 

I  PAGE 

1.  Extension  or  figure. 

Matter— State  of  aggregation — Solids — Cohesion — Force — 
Crystallized,  amorphous,  polymorphous,  isoinorphous  sub- 
stances —Liquids — Gases — Law  of  Mariotte  ....  17-21 

2.  Divisibility. 

Mechanical  comminution — Action  of  heat  on  matter — 
Molecular  theory — Law  of  Avogadro — Motion  of  molecules, 
heat— Melting,  boiling,  distillation,  sublimation — Thermo- 
meters-Specific heat  .  .  .  .  .  .  .  .  21-28 

3.  Gravitation.  ^ 

Action  of  gravitation — Weight,  specific  weight — Hydro- 
meters—Weight  of  gases— Barometer — Changes  in  the  atmo- 
spheric pressure — Influence  of  pressure  on  state  of  aggregation  28-31 

4.  Porosity. 

Nature  of  porosity — Surface,  surface-action — Adhesion — 
Capillary  attraction  —  Absorption — Diffusion — Dialysis — In- 
destructibility    .  .  .  32-36 


II. 

PRINCIPLES  OF  CHEMISTRY.    RESULTS  OF  THE  ATTRACTION 
BETWEEN  ATOMS. 

5.  Chemical  divisibility. 

Decomposition  by  heat — Elements— Compound  substances — 
Chemical  affinity — Atoms — Chemistry — Atomic  and  molecular 
weight— Chemical  symbols  and  formulas 37-42 

6.  Laws  of  chemical  combination. 

Law  of  the  constancy  of  composition — Law  of  multiple  pro- 
portions—Law of  chemical  combination  by  volume— Law  of 
equivalents— Quantivalence,  valence  .  ...  42-48 


Vi  CONTENTS. 

PAGE 

7.  Determination  of  atomic  and  molecular  weights. 

Determination  of  atomic  weights  by  chemical  decomposition, 
by  means  of  specific  weights  of  gases  or  vapors,  by  means  of 
specific  heat — Determination  of  molecular  weights— Raoult's 
law „  48-53 

8.  Decomposition  of  compounds.    Groups  of  compounds. 

Decomposition  by  heat,  light,  and  electricity — Mutual  action 
of  substances  upon  each  other — The  nascent  state — Analysis 
and  synthesis — Acid,  basic,  and  neutral  substances— Salts — 
Eesidues,  radicals 53-60 

9.  General  remarks  regarding  elements. 

Eelative  importance  of  different  elements — Classification  of 
elements— Metals  and  non-metals — Natural  groups  of  elements 
— Mendel ejefPs  periodic  law— Physical  properties  of  elements 
Allotropic  modifications— Relationship  between  elements  and 
the  compounds  formed  by  their  union — Nomenclature — Writ- 
ing chemical  equations— How  to  study  chemistry  .  .  .  60-70 

III. 

NON-METALS  AND  THEIR  COMBINATIONS. 

Symbols,  atomic  weights,  and  derivation  of  names— Occur- 
rence in  nature — Time  of  discovery — Valence  .  .  .  71-72 

10.  Oxygen. 

History — Occurrence  in  nature — Preparation — Physical  and 
chemical  properties— Combustion — Ozone  ....  73-77 

11.  Hydrogen. 

History— Occurrence  in  nature — Preparation— Properties  — 
Water — Mineral  waters — Drinking-water— Distilled  water — 
Hydrogen  dioxide 78-84 

12.  Nitrogen. 

Occurrence  in  nature — Preparation — Properties — Atmo- 
spheric air— Ammonia — Compounds  of  nitrogen  and  oxygen — 
Nitrogen  monoxide — Nitric  acid ;  tests  for  it  .  .  .  .  84-91 

13.  Carbon. 

Occurrence  in  nature — Properties— Diamond — Graphite — 
Tests  for  carbon— Carbon  dioxide— Carbonic  acid — Tests  for 
carbonic  acid  —  Carbon  monoxide — Compounds  of  carbon  and 
hydrogen — Flame — Silicon — Silicic  acid — Boron,  boric  acid  ; 
tests  for  it 92-99 

14.  Sulphur. 

Occurrence  in  nature — Properties — Crude,  sublimed,washed, 
and  precipitated  sulphur — Sulphur  dioxide— Sulphurous  acid  ; 
tests  for  it— Sulphur  trioxide— Sulphuric  acid ;  its  manufac- 
ture and  properties — Tests  for  sulphates— Sulpho-acids — 
Pyrosulphuric  acid — Thiosulphuric  acid— Hydrogen  sulphide ; 
tests  for  it— Carbon  disulphide— Selenium— Tellurium  .  .  100-108 


CONTENTS. 


vn 


15.  Phosphorus. 

Occurrence  in  nature — Manufacture,  properties,  and  modi- 
fications—Poisonous properties  and  detection  in  cases  of 
poisoning —Oxides  of  phosphorus — Phosphorous  acid;  tests  for 
it — Metaphosphoric,  pyrophosphoric,  orthophosphoric  acids  ; 
tests  for  them — Hypophosphorous  acid ;  tests  for  it — Hydrogen 
phosphide 109-117 

16.  Chlorine. 

Haloids  or  halogens — Preparation  and  properties  of  chlorine 
— Chlorine  water — Hydrochloric  acid;  tests  for  it — Nitro- 
hydrochloric  acid — Compounds  of  chlorine  with  oxygen — 
Hypochlorous  acid— Chloric  acid ;  tests  for  it  .  .  .  .  117-123 

17.  Bromine.    Iodine.    Fluorine. 

Bromine — Hydrobromie*  acid — Tests  for  bromides — Hypo- 
bromic  and  bromic  acid — Iodine — Hydriodic  acid — Tests  for 
iodine  and  iodides — Fluorine — Hydrofluoric  acid  .  .  .  123-128 


IV. 


METALS  AND  THEIR  COMBINATIONS. 


18.  General  remarks  regarding  metals. 

Derivation  of  names,  symbols,  and  atomic  weights — Melting- 
points,  specific  gravities,  time  of  discovery,  valence,  occur- 
rence in  nature,  classification,  and  general  properties  of  metals  129-134 

19.  Potassium. 

General  remarks  regarding  the  alkali  metals — Occurrence  in 
nature — Potassium  hydroxide,  carbonate,  bicarbonate,  nitrate, 
chlorate,  sulphate,  sulphite,  hyposulphite,  iodide,  bromide — 
Analytical  reactions 134-141 

20.  Sodium. 

Occurrence  in  nature — Sodium  hydroxide,  chloride,  car- 
bonate, bicarbonate,  sulphate,  sulphite,  thiosulphate,  phos- 
phate, nitrate,  borate — Analytical  reactions — Lithium  .  .  141-146 

21.  Ammonium. 

General  remarks — Ammonium  chloride,  carbonate,  sulphate, 
nitrate,  phophate,  iodide,  bromide,  and  sulphide — Analytical 
reactions — Summary  of  analytical  characters  of  the  alkali- 
metals  146-149 

22.  Magnesium. 

General  remarks— Occurrence  in  nature — Metallic  mag- 
nesium— Magnesium  carbonate,  oxide,  sulphate,  sulphite — 
Analytical  reactions  .........  150-152 


Vlll 


CONTENTS. 


23.  Calcium. 

General  remarks  regarding  alkaline  earths — Occurrence  in 
nature — Calcium  oxide,  hydroxide,  carbonate,  sulphate,  phos- 
phate, acid  phosphate,  and  hypophosphite — Bone-black  and 
bone-ash — Chlorinated  lime,  calcium  chloride  and  bromide — 
Sulphurated  lime — Analytical  reactions  for  calcium — Barium 
and  strontium  ;  their  salts  and  analytical  reactions — Summary 
of  analytical  characters  of  the  alkaline  earth-metals  .  .  152-159 

24.  Aluminum. 

Occurrence  in  nature — Metallic  aluminum — Alum — Alumi- 
num hydroxide,  oxide,  sulphate,  and  chloride — Clay — Glass — 
Ultramarine  — Analytical  reactions — Cerium  — Summary  of 
Analytical  characters  of  the  earth-metals  and  chromium  .  159-165 

25.  Iron. 

General  remarks  regarding  the  metals  of  the  iron  group — 
Occurrence  in  nature  —  Manufacture  of  iron — Properties — 
Eeduced  iron — Ferrous  and  ferric  oxides,  hydroxides,  and 
chlorides — Dialyzed  iron— Ferrous  iodide,  bromide,  sulphide, 
and  sulphate— Ferric  sulphate  and  nitrate— Ferrous  carbonate, 
phosphate,  and  hypophosphite— Analytical  reactions  .  .  165-174 

26.  Manganese.    Chromium.    Cobalt.    Nickel. 

Manganese;  its  oxides  and  sulphate — Potassium  perman- 
ganate— Manganese  reactions — Chromium — Potassium  dichro- 
mate — Chromium  trioxide — Chromic  oxide  and  hydroxide — 
Reactions  for  chromium  compounds — Cobalt  and  nickel  .  174-180 

27.  Zinc. 

Occurrence  in  nature —Metallic  zinc— Zinc  oxide,  chloride, 
bromide,  iodide,  carbonate,  sulphate,  and  phosphide — Analy- 
tical reactions — Antidotes — Cadmium — Summary  of  analytical 
characters  of  metals  of  the  iron  group 180-184 

28.  Lead.    Copper.    Bismuth. 

General  remarks  regarding  the  metals  of  the  lead  group — 
Lead— Lead  oxides,  nitrate,  carbonate,  iodide— Poisonous 
properties  of  lead— Antidotes — Lead  reactions — Copper — 
Cupric  and  cuprous  oxide — Cupric  sulphate  and  carbonate — 
Ammonio-copper  compounds — Poisonous  properties  and  anti- 
dotes— Copper  reactions — Bismuth — Bismuthyl  nitrate,  car- 
bonate, and  iodide— Bismuth  reactions 185-193 

29.  Silver.    Mercury. 

Silver — Silver  nitrate,  oxide,  iodide — Antidotes — Silver 
reactions — Mercury — Mercurous  and  mercuric  oxides,  chlo- 
rides, iodides,  sulphates,  nitrates,  sulphides— Ammoniated 
mercury — Antidotes —Mercury  reactions —Summary  of  analy- 
tical characters  of  metals  of  the  lead  group  ....  193-204 


CONTENTS. 

30.  Arsenic. 

General  remarks  regarding  the  metals  of  the  arsenic  group 
— Arsenic — Arsenous  and  arsenic  oxides  and  acids— Sodium 
arsenate  —  Hydrogen  arsenide  —  Sulphides  of  arsenic —Arsenous 
iodide — Analytical  reactions — Preparatory  treatment  of  or- 
ganic matter  for  arsenic  analysis— Antidotes  .... 

31.  Antimony.    Tin.    Gold.    Platinum.    Molybdenum. 

Antimony — Trisulphide,  oxysulphide,  and  pentasulphide  of 
antimony — Antimonous  chloride  and  oxide — Antidotes— Anti- 
mony reactions— Tin — Stannous  and  stannic  chloride— Tin 
reactions  —  Gold  —  Platinum  —  Molybdenum  —  Summary  of 
analytical  characters  of  metals  of  the  arsenic  group 


IX 


PAGE 


205-214 


215-221 


Y. 


ANALYTICAL   CHEMISTRY. 

32.  Introductory  remarks  and  preliminary  examination. 

General  remarks— Apparatus  needed  for  qualitative  analysis 
— Reagents  needed— General  mode  of  proceeding  in  qualitative 
analysis— Use  of  reagents— Preliminary  examination — Phys- 
ical properties  —Action  on  litmus  —Heating  on  platinum  foil 
— Heating  on  charcoal  alone  and  mixed  with  sodium  car- 
bonate—Flame-tests— Colored  borax-beads— Liquefaction  of 
solid  substances — Table  I. :  Preliminary  examination 


222-232 


33.  Separation  of  metals  in  different  groups. 

General  remarks  — Group  reagents —Acidifying  the  solution 
— Addition  of  hydrogen  sulphide — Separation  of  the  metals  of 
the  arsenic  group  from  those  of  the  lead  group — Addition  of 
ammonium  sulphide  and  ammonium  carbonate — Table  II. : 
Separation  of  metals  in  different  groups 233-238 

34.  Separation  of  the  metals  of  each  group. 

Table  III. :  Treatment  of  the  precipitate  formed  by  hydro- 
chloric acid — Treatment  of  the  precipitate  formed  by  hydrogen 
sulphide — Table  IV. :  Treatment  of  that  portion  of  the  hydro- 
gen sulphide  precipitate  which  is  insoluble  in  ammonium 
sulphide — Table  V. :  Treatment  of  that  portion  of  hydrogen 
sulphide  precipitate  which  is  soluble  in  ammonium  sulphide 
— Table  VI. :  Treatment  of  the  precipitate  formed  by  ammo- 
nium hydroxide  and  sulphide — Table  VII. :  Treatment  of  the 
precipitate  formed  by  ammonium  carbonate — Table  VIII.  : 
Detection  of  the  alkalies  and  of  magnesium  ....  238-241 

35.  Detection  of  acids. 

General  remarks— Detection  of  acids  by  means  of  the  action 
of  strong  sulphuric  acid— Table  IX. :  Preliminary  examina- 
tion for  acids— Detection  of  acids  by  means  of  reagents  added 


CONTENTS. 


to  their  neutral  or  acid  solution — Table  X. :  Detection  of  the 
more  important  acids  by  means  of  reagents  added  to  the  solu- 
tion—Table XL:  Systematically  arranged  table,  showing  the 
solubility  and  insolubility  of  inorganic  salts  and  oxides — 
Table  XII.:  Table  of  solubility 242-248 

36.  Methods  for  quantitative  determinations. 

General  remarks  —  Gravimetric  methods  —  Volumetric 
methods— Standard  solutions — Different  methods  of  volu- 
metric determination— Indicators — Titration— Acidimetry  and 
alkalimetry — Normal  acid  and  alkali  solution— Oxidimetry — 
Potassium  permanganate  and  dichromate— lodimetry — Solu- 
tions of  iodine,  sodium  thiosulphate,  bromine,  silver  nitrate, 
sodium  chloride,  and  potassium  sulphocyanate — Gas  analysis  249-271 

37.  Detection  of  impurities  in  official  inorganic  chemical  prepara- 

tions. 

General  remarks — Official  chemicals  and  their  purity — Tests 
as  to  identity — Qualitative  tests  for  impurities— Quantitative 
tests  for  the  limit  of  impurities 271-276 


VI. 


CONSIDERATION  OF  CARBON  COMPOUNDS,  OR   ORGANIC 
CHEMISTRY. 

38.  Introductory  remarks.    Elementary  analysis. 

Definition  of  organic  chemistry  — Elements  entering  into  or- 
ganic compounds — General  properties  of  organic  compo.unds 
— Difference  in  the  analysis  of  organic  and  inorganic  substances 
— Qualitative  analysis  of  organic  substances —Ultimate  or 
elementary  analysis — Determination  of  carbon,  hydrogen, 
oxygen,  nitrogen,  sulphur,  and  phosphorus — Determination  of 
atomic  composition  from  results  obtained  by  elementary 
analysis— Empirical  and  molecular  formulas — Rational,  con- 
stitutional, structural,  or  graphic  formulas  ....  277-285 

39.  Constitution,  decomposition,  and   classification  of  organic 

compounds. 

Radicals  or  residues— Chains— Homologous  series— Types — 
Substitution  —  Derivatives  —  Isomerism — Metamerism— Poly- 
merism — Various  modes  of  decomposition — Action  of  heat 
upon  organic  substances — Dry  or  destructive  distillation — 
Action  of  oxygen  upon  organic  substances — Combustion — 
Decay — Fermentation  and  putrefaction — Antiseptics,  disin- 
fectants, and  deodorizers — Action  of  chlorine,  bromine,  nitric 
acid,  alkalies,  dehydrating  and  reducing  agents  upon  organic 
substances— Classification  of  organic  compounds  .  .  .  286-297 


CONTENTS. 


XI 


40.  Hydrocarbons. 

Occurrence  in  nature — Formation  of  hydrocarbons— Prop- 
erties— Paraffin  or  methane  series — Methane — Coal — Natural 
gas — Coal-oil,  petroleum — Illuminating  gas — Coal-tar — Ole- 
fines— Benzene  series  or  aromatic  hydrocarbons — Volatile  or 
essential  oils 298-307 

41.  Alcohols. 

Constitution  of  alcohols— Occurrence  in  nature — Formation 
and  properties  of  alcohols — Monatomic  normal  alcohols — 
Methyl  alcohol— Ethyl  alcohol —Alcoholic  liquors— Wines, 
beer,  spirits— Amy  1  alcohol — Glycerin — Nitro-glycerin — Phe- 
nols    .  307-314 

42.  Aldehydes.    Haloid  derivatives. 

Aldehydes — Acetic  aldehyde  —  Paraldehyde  —  Trichloral- 
dehyde—  Chloral  hydrate  -*  Chloroform —  Bromoform — lodo- 
form— Ethyl  bromide— Sulphonal 315-321 

43.  Monobasic  fatty  acids. 

General  constitution  of  organic  acids— Occurrence  in  nature 
— Formation  of  acids — Properties — Fatty  acids — Formic  acid 
Acetic  acid— Vinegar — Reactions  for  acetates — Acetate  of 
potassium,  sodium,  zinc,  iron,  lead,  and  copper — Acetone — 
Butyric  acid  — Valerianic  acid  and  its  salts — Oleic  acid  .  .  322-330 

44.  Dibasic  and  tribasic  organic  acids. 

Oxalic  acid,  oxalates,  and  analytical  reactions  — Tartaric 
acid;  analytical  reactions -Potassium  tartrate — Potassium- 
sodium  tartrate— Antimony-potassium  tartrate— Action  of  cer- 
tain organic  acids  upon  certain  metallic  oxides  — Scale  com- 
pounds— Citric  acid;  analytical  reactions — Citrates — Lactic 
acid— Ferrous  lactate  .  ....  331-339 

45.  Ethers. 

Constitution — Formation  of  ethers — Occurrence  in  nature — 
General  properties  —Ethyl  ether — Acetic  ether— Ethyl  nitrite 
— Amyl  nitrite — Fats  and  fat  oils — £oap—  Lanolin  .  .  .  339-346 

46.  Carbohydrates. 

Constitution — Properties — Occurrence  in  nature — Groups  of 
carbohydrates — Grape-sugar;  tests  for  it — Fruit-sugar — Inosite 
— Cane-sugar  — Milk-sugar  — Starch  — Dextrin — Gums — Cellu- 
lose— Nitro-cellulose— Glycogen—  Glucosides — Digitalin — My- 
ronic  acid  ...........  345-355 

47.  Amines  and  amides.    Cyanogen  compounds. 

Forms  of  nitrogen  in  organic  compounds — Amines — Amides 
— Amido-acids — Formation  of  amines  and  amides — Occurrence 
in  nature — Cyanogen  compounds— Dicyanogen— Hydrocyanic 
acid — Potassium,  silver,  and  mercuric  cyanides — Reactions  for 
cyanides — Antidotes — Cyanic  acid— Sulphocyanic  acid — Me- 
tallocyanides — Potassium  ferrocyanide— Reactions  for  ferro- 
cyanides— Potassium  ferricyanide — Nitro-cyan-methane  .  .  355-366 


Xll 


CONTENTS 


48.  Benzene  series.    Aromatic  compounds. 

General  remarks— Benzene  series  of  hydrocarbons— Benzene 
—  Nitro-benzene  —  Benzene-derivatives  —  Phenols  —  Carbolic 
acid;  tests  for  it— Creosote— Sulphocarbolic  acid— Picric  acid — 
Phenacetine— Eesorcin— Cymene — Terpenes — Resins  —  India- 
rubber  — Gutta  percha—  Stearoptenes — Camphors — Menthol — 
Thymol — Benzoic  acid — Oil  of  bitter  almond — Salicylic  acid 
— Salol  — -Phtalic  acid — Gallic  acid— Pyrogallol — Tannin — 
Naphtalene— Naphtol—  Santonin  . 

49.  Benzene-derivatives  containing  nitrogen. 

Aniline  —Aniline  dyes  — Antifebrine  —  Antipyrine — Saccha- 
rine— Pyrrole — Pyridine — Quinoline — Kairine — Thalline 


364-381 


382-387 


50.  Alkaloids. 

General  remarks — General  properties  of  alkaloids— Mode  of 
obtaining  them— Antidotes— Detection  in  cases  of  poisoning — 
List  of  important  alkaloids— Sparteine — Coniine — Nicotine — 
Opium— Morphine;  its  salts  and  reactions— Codeine— Narco- 
tine  and  narceine— Meconic  acid— Cinchona  alkaloids — Qui- 
nine; its  salts  and  reactions— Quinidine — Cinchonine— Cin- 
chonidine — Strychnine  and  its  reactions — Brucine — Atropine- 
Hyoscyamine  —  Hyoscine — Cocaine  and  its  reactions— Aconi- 
tine  —  Veratrine  —  Hydrastine  —  Hydrastinine  —  Berberine — 
Physostigmine  —  Pilocarpine  —  Caffeine  —  Theobromine  —  Pi- 
perm— Ptomaines — Leucomaines— Toxalbumins — Antitoxins  .  387-410 

51.  Albuminous  substances  or  proteids. 

Occurrence  in  nature— General  properties— Analytical  re- 
actions— Classification — Native  or  true  albumins — Globulins — 
Derived  albumins  or  albuminates — Fibrins — Coagulated  pro- 
teids — Albumoses  —  Peptones  — Amyloid  substance  — Haemo- 


globin —Enzymes — Pepsin  — Pancreatin — Gelatinoids 


410-419 


.VII. 

PHYSIOLOGICAL  CHEMISTEY. 

52.  Chemical  changes  in  plants  and  animals. 

General  remarks— Difference  between  vegetable  and  animal 
life — Formation  of  organic  substances  by  the  plant — Decompo- 
sition of  vegetable  matter  in  the  animal  system — Animal  food 
— Nutrition  of  animals,  digestion — Absorption — Respiration — 
Waste  products  of  animal  life — Chemical  changes  after  death  .  420-429 

53.  Animal  fluids  and  tissues. 

Constituents  of  the  animal  body — Blood — Examination  of 
blood-stains — Chyle — Lymph — Saliva — Gastric  juice ;  clinical 
examination  of  it — Bile — Biliary  pigments — Biliary  acids ;  tests 
for  them — Cholesterin — Lecithin — Pancreatic  juice — Feces — 
Bone — Teeth — Hair,  nails,  etc. — Mucus — Muscles — Brain  .  429-445 


CONTENTS. 


xm 


54.  Milk. 

Properties  and  composition — Changes  in  milk — Butter — 
Cheese — Adulteration  of  milk— Testing  milk — Lactometer, 
creamometer,  lactoscope — Analysis  of  milk  ....  445-451 

55.  Urine  and  its  normal  constituents. 

Secretion  of  urine  —  General  properties  —  Composition  — 
Urea;  its  properties  and  determination — Uric  acid;  tests  for  it 
— Hippuric  acid ;  tests  for  it 452-459 

56.  Examination  of  normal  and  abnormal  urine. 

Points  to  be  considered  in  the  analysis  of  urine — Color — In- 
dican — Odor— Eeaction — Specific  gravity — Determination  of 
total  solids,  and  of  total  organic  and  inorganic  constituents — 
Detection  and  estimation  of  albumin — Blood — Detection  and 
estimation  of  sugar— Detec^on  of  bile — Diazo-reaction — Urin- 
ary deposits — Urinary  calculi — Microscopical  examination  of 
urinary  sediments  . 459-482 


APPENDIX. 


Table  of  weights  and  measures 
Table  of  elements 
Index   , 


483 

485 
487 


LIST  OF  ILLUSTRATIONS, 


FIG.  PAGE 

I,  2.  Structure  of  matter 22,  23 

3.  Thermometric  scales 27 

4.  Dialyzer .35 

5.  Apparatus  for  the  decomposition  of  mercuric  oxide     ....      37 

6.  Apparatus  for  generating  oxyeren  .         .         . 75 

7.  Apparatus  for  generating  hydaogen       .  .         .         .         .         .79 

8.  Apparatus  for  generating  ammonia       .......      86 

9.  Distillation  of  nitric  acid      .........      90 

10.  Structure  of  flame 97 

II.  Apparatus  for  making  sulphurous  acid 102 

12.  Apparatus  for  detection  of  phosphorus         .         .         .         .         .        .112 

13-16.  Detection  of  arsenic 210-213 

17-21.  Apparatus  for  analytical  operations 223,  224 

22.  Heating  of  solids  in  bent  glass  tube .  228 

23.  Heating  on  charcoal  by  means  of  blowpipe 228 

24.  Washing  and  decanting  in  agate  mortar 229 

25.  Platinum  wire  for  blowpipe  experiments 230 

26.  27.  Apparatus  for  generating  hydrosulphuric  acid        ....  235 

28.  Drying-oven 250 

29.  Desiccator 251 

30.  Watch-glasses  for  weighing  niters 251 

31.  Liter  flask 252 

32.  Pipettes 252 

33.  Mohr's  burette  and  clamp 253 

34.  Mohr's  burette  and  holder     . .253 

35.  Gay  Lussac's  burette 254 

36.  Titration 259 

37.  Flask  for  dissolving  iron 263 

38.  Gas-furnace  for  organic  analysis 281 

39.  Flasks  for  fractional  distillation 299 

40.  Liebig's  condenser,  with  flask       ........  311 

41.  Apparatus  for  estimation  of  urea  ........  456 

42  Urinometer    ........••••  462 

43.  Nitric  acid  test  for  urine •  467 

44.  Urinary  sediments         .......«••    481 


(xv) 


COLORED  PLATES. 


FACING 
PAGE 

PLATE         I.  Compounds  of  iron,  cobalt,  and  nickel       ....  174 

II.  Compounds  of  manganese  and  chromium  .         .         .         .180 

"          III.  Compounds  of  copper,  lead,  knd  bismuth  ....  190 

IV.  Compounds  of  silver  and  mercury      .         .         .         .         .  202 

V.  Compounds  of  arsenic,  antimony,  and  tin  ....  210 

VI.     Benzene  derivatives 370 

VII.  Eeactions  of  alkaloids          ...                 ...  388 

"       VIII.  Urine  and  tests  for  its  constituents                                         ,  460 


ABBREVIATIONS. 

c.c.          =  Cubic  centimeter. 

B.  P.      =  Boiling-point. 

F.  P.      =  Fusing-point. 

Sp.  gr.    =  Specific  gravity. 

U.  S.  P.  =  United  States  Pharmacopoeia. 


(xvi) 


PRACTICAL  CHEMISTRY, 

PHARMACEUTICAL  AND   MEDICAL. 


INTRODUCTION. 

FUNDAMENTAL  PROPERTIES  OF  MATTER.    RESULTS  OF  THE 

ATTRACTIONS  BETWEEN  MASSES,  SURFACES, 

AND  MOLECULES. 


As  the  science  of  Chemistry  has  for  its  object  the  study  of  the 
nature  of  all  substances,  or  of  all  varieties  of  matter,  it  is  necessary 
first  to  consider  some  of  the  properties  which  belong  to  every  kind  of 
matter,  and  are  known  as  essential  or  fundamental  properties.  The 
fundamental  properties  of  matter  having  a  special  interest  for  those 
studying  chemistry  are :  extension,  divisibility,  gravitation,  porosity,  and 
indestructibility. 

I.    EXTENSION  OR  FIGURE. 

Matter  is  anything  occupying  space,  and  this  property  is  known  as 
extension.  All  bodies,  without  exception,  fill  a  certain  amount  of 
space ;  they  all  have  length,  breadth,  and  thickness.  That  portion  of 
matter  lying  within  the  surrounding  surface  of  a  body  is  called  its 
mass.  We  distinguish  three  different  conditions  of  matter,  namely : 
Solids,  Liquids,  and  Gases.  These  conditions  of  matter  are  known  as 
the  three  states  of  aggregation,  and  we  will  now  consider  the  peculiar- 
ities of  matter  when  existing  in  either  of  these  states. 

Solid  state.  Solids  are  distinguished  by  a  self-subsistent  figure. 
A  solid  substance  forms  for  itself,  as  it  were,  a  casing  in  which  its 

2  (17) 


1  8  INTR  OD  UCTION. 

smallest  particles1  are  enclosed.  The  question  arises,  By  what  means 
are  these  particles  connected  ?  how  are  they  kept  together  ?  No  other 
answer  can  be  given  than  that  the  particles  themselves  attract  each 
other  to  such  an  extent  that  force  is  necessary  to  make  them  alter 
their  relative  positions.  We  see,  consequently,  that  some  form  of 
attraction  or  attractive  power  is  acting  between  the  particles  of  a  solid 
mass,  and  we  call  this  kind  of  attraction  cohesion,  to  distinguish  it 
from  other  forms  of  attraction. 

The  external  appearance  or  the  figure  of  solid  bodies  is  various. 
It  may  be  an  irregular  or  a  natural  regular  figure.  Of  these  two 
forms,  only  the  latter  is  here  of  interest,  as  it  includes  all  the  different 
crystallized  substances. 


Force  may  be  defined  as  the  action  of  one  body  upon  another 
body,  or  as  the  action  of  particles  of  matter  upon  other  particles 
either  of  the  same  or  of  another  body.  Strictly  speaking,  we  may 
say  that  facca  .is.the-_cause  tending  to  produce,  change,  or  arrest 
motion  ;  or  it  is  any  action  upon  matter  changing  or  tending  to  change 
its  form  or  position. 

In  many  cases  force  manifests  itself  as  an  attractive  power;  for  instance,  in 
the  case  of  cohesion  mentioned  above,  but  also  in  adhesion,  gravitation,  etc. 
Forces  often  give  rise  to  motion  (as  in  the  case  of  heat  and  electricity),  and 
also  to  a  great  variety  of  changes  in  matter.  The  three  different  states  of 
aggregation  are  due  to  the  relative  intensity  of  two  opposing  forces,  one  —  that 
of  molecular  attraction—  which  tends  to  draw  the  molecules  together,  and  a 
second  one  —  that  of  heat  —  which  tends  to  separate  the  molecules  from  one 
Another. 

Energy  of  a  body  is  its  capacity  of  doing  work,^and  is  measured  by  the  pro- 
duct of  the  force  acting  and  the  distance  through  which  it  acts. 

Crystals  are  solid  substances  bounded  by  plane  surfaces  symmetri- 
cVlly  arranged  according  to  fixed  laws^N  In  explaining  the  formation 
of  crystals  we  have  to  assume  that  the  particles  are  endowed  with  the 
power  of  attracting  one  another  in  certain  directions,  thereby  building 
themselves  up  into  geometrical  forms. 

The  first^cQndition  essential  to  the  formation  of  crystals  is  the  possi- 
bility of  freejnotion  of  the  smallest  particles  of  the  matter  to  be  crys- 
tallized; in  that  case  only  will  they  be  able  to  attract  each  other  in 
such  a  way  as  to  assume  a  regular  shape,  or  form  crystals.  Particles 
of  a  solid  mass  can  move  freely  only  after  they  have  been  transferred 

1  It  will  be  shown  later  that  all  matter  is  supposed  to  consist  of  smallest  particles,  which  we 
call  molecules. 


EXTENSION  OE  FIGURE.  19 

to  the  liquid  or  gaseous  state.  There  are  two  different  methods  of 
liquefaction,  viz.,  by  means  of  heat  (melting),  or  solution  in  some 
suitable  agent  (dissolving).  In  the  liquid  condition  thus  produced, 
the  smallest  particles  can  follow  their  own  attraction,  and  unite  to 
form  crystals  on  removal  of  the  cause  of  liquefaction  (heat  or  solvent). 

If  two  or  more  (non-isomorphous)  substances — for  instance,  common  salt 
and  Glauber's  salt — be  dissolved  together  in  water,  and  the  solution  be  allowed 
to  crystallize,  the  attraction  of  like  particles  for  one  another  will  be  readily 
noticed  by  the  formation  of  distinct  crystals  of  common  salt  alongside  of 
crystals  of  Glauber's  salt;  neither  do  the  particles  of  common  salt  help  to 
build  up  a  crystal  of  Glauber's  salt,  nor  the  particles  of  the  latter  a  crystal  of 
common  salt.  Advantage  is  taken  of  this  property  in  separating  (by  crystal- 
lization) solids  from  each  other,  ^  4ien  they  are  contained  in  the  same  solution. 

Not  all  matter  can  form  crystals ;  some  substances  never  have  been 
obtained  in  a  crystallized  state,  such  as  starch,  gum,  glue,  etc.  A 
solid  substance  showing  no  crystalline  structure  whatever  is  called 
amorphous. 

nSbme  substances  capable  of  crystallization  may  be  obtained  also  in 
an  amorphous  state  (carbon,  sulphur).  Other  substances  are  capable 
of  assuming  different  crystalline  shapes  under  different  conditions. 
Thus  sulphur,  when  liquefied  by  heat,  assumes,  on  cooling,  a  shape 
different  from  the  sulphur  crystallized  from  a  solution.  One  and  the 
same  substance  under  the  same  conditions  always  assumes  the  same 
shape.  Substances  capable  of  assuming  in  solidifying  two  or  more 
different  shapes  or  conditions,  are  said  to  be  dimorphous  and  poly- 
morphous, respectively.  When  substances  of  different  kinds  crystallize 
in  exactly  the  same  form  we  call  them  ixomorphous  (sulphate  of 
magnesium  and  sulphate  of  zinc).  If  two  isomorphous  substances 
be  contained  in  one  solution,  they  will  crystallize  together,  and  the 
crystals  are  made  up  of  particles  of  both  substances. 

Characteristic  properties  of  solids.  Solid  substances  show  a 
great  variety  of  properties  caused  by  the  differences  in  the  cohesion 
of  the  particles  (molecules)  composing  the  substances,  and  accordingly 
we  distinguish  between  hard  and  soft,  brittle,  tenacious,  malleable, 
and  ductile  substances. 


Hardness  is  that  property  in  virtue  of  which  some  bodies  resist  attempts  to 
force  passage  between  their  particles,  or  which  enables  solids  to  resist  the  dis- 
placement of  their  particles.  Diamond  and  quartz  are  extremely  hard,  while 
wax  and  lead  are  comparatively  soft. 


20  INTRODUCTION. 

Brittleness  is  that  property  of  solids  which  causes  them  to  be  broken  easily 
when  external  force  is  applied  to  them.  Glass,  sulphur,  coal,  etc.,  are  brittle. 

Tenacity  is  that  property  in  virtue  of  which  solids  resist  attempts  to  pull 
their  particles  asunder.  Iron  is  one  of  the  most  tenacious  substances. 

Malleability,  possessed  by  some  solids,  is  the  property  in  virtue  of  which  they 
may  be  hammered  or  rolled  into  sheets.  Gold  is  so  malleable  that  it  may  be 
beaten  into  sheets  so  thin  that  it  would  require  about  300,000  laid  upon  one 
another  to  measure  one  inch. 

Ductility  is  the  property  in  virtue  of  which  some  solids  may  be  drawn  into 
wire  or  thin  sheets — as,  for  instance,  copper,  iron,  and  platinum. 

Liquid  state.  The  characteristic  features  of  liquids  are,  that  they 
have  no  self-subsistent  figure;  that  they  consequently  require  some 
vessel  to  hold  them ;  and  that  they  present  a  horizontal  surface.  While 
in  a  solid  substance  the  smallest  parties  are  held  together  by  cohe- 
sion to  such  an  extent  that  they  cannot  change  their  relative  position 
without  force,  in  a  liquid  this  cohesion  acts  with  much  less  energy 
and  permits  of  a  comparatively  free  motion  of  the  particles;  the 
repellant  and  attractive  forces  nearly  balance  each  other  in  a  liquid. 
That  cohesion  is  not  altogether  suspended  in  a  liquid  is  shown  by  the 
formation  of  drops  or  round  globules,  which,  of  course,  consist  of  a 
large  number  of  smallest  particles.  If  there  were  no  cohesion  at  all 
between  these  particles  of  a  liquid,  drops  could  not  be  formed. 

The  terms  semi-solid  and  semi-liquid  substances  are  used  for  bodies  occupy- 
ing a  position  intermediate  between  true  solids  and  fluids;  butter,  asphalt, 
amorphous  sulphur,  are  instances  of  this  kind. 

Gaseous  state.  Matter  in  the  gaseous  state  has  absolutely  no 
self-subsistent  figure.  Gases  fill  any  vessel  or  room  entirely  ;  the 
smallest  particles  show  the  highest  degree  of  mobility  and  move 
freely  in  every  direction.  Cojiesioji.  js  entirely  suspended  in  gases ; 
indeed,  the  smallest  particles  exhibit  toward  each  other  an  infinite 
repulsion,  so  that  force  is  necessary  to  restrain  them  within  any  given 
bounds  whatever.  It,  therefore,  follows  that  gases  set  up  and  main- 
tain a  pressure  against  the  walls  of  vessels  enclosing  them.  This 
characteristic  property,  possessed  by  all  gases,  is  known  as  elasticity, 
or,  better,  as  tension,  and  is  so  unvarying  that  a  law  has  been  estab- 
lished in  relation  to  it.  This  law  is  known  as  the  Law  of  Mariotte 
(though  really  discovered  by  Boyle,  of  England,  in  1661),  and  may 
be  expressed  thus:  {'The  volume  of  a  gas  is  inversely  as  the  pressure ; 
the  density  and  elastic  force  are  directly  as  the  pressure  and  inversely 
as  the  volume.  J  For  instance :  If  a  vessel  contains  one  cubic  foot  of 
a  gas  under  a  pressure  of  ten  pounds,  the  volume  will  be  reduced  to 


DIVISIBILITY.  21 

one-half,  one-tenth,  or  one-hundredth  of  one  cubic  foot,  if  the  press- 
ure be  increased  to  20,  100,  or  1000  pounds  respectively.  On  the 
contrary,  the  gas  will  expand  to  2,  10,  or  100  cubic  feet,  if  the 
pressure  is  reduced  to  5,  1,  or  one-tenth  pound  respectively.  Vapors, 
produced  by  evaporation  of  liquids  or  solids,  have  the  same  properties 
as  gases. 

2.    DIVISIBILITY. 

Mechanical  comminution.  All  matter  admits  of  being  sub- 
divided into  smaller  particles,  and  this  property  is  called  divisibility. 
The  processes  by  which  we  accomplish  the  comminution  of  a  solid 
substance  may  be  of  a  mechljlrical  nature,  such  as  cutting,  crushing, 
grinding,  but  beside  these  modes  of  subdivision  we  have  other  agents 
or  causes  by  which  matter  may  be  divided  into  smaller  particles,  and 
one  of  these  agents  is  heat. 

Action  of  heat  on  matter.  Let  us  take  a  piece  of  ice  and 
convert  it,  by  means  of  mortar  and  pestle,  into  a  very  fine  powder. 
When  the  smallest  particle  of  this  finely  powdered  ice  is  placed 
under  the  microscope  and  heat  applied,  we  shall  observe  that  it 
becomes  liquid,  thus  proving  that  it  was  capable  of  further  sub- 
division, that  it  consisted  of  smaller  particles,  which  have  now  by 
the  action  of  heat  become  movable.  By  further  applying  heat  to  the 
liquid  particle  of  water  we  may  convert  it  into  a  gas  or  vapor,  which 
will  escape  into  the  air,  or  which  we  may  collect  in  an  empty  flask. 
The  flask  will  be  filled  completely  by  this  water-gas  (or  steam) 
obtained  by  vaporizing  that  minute  particle  of  ice-dust.  This  fact 
demonstrates  that  mechanical  comminution  does  not  carry  us  beyond 
a  certain  degree  of  subdivision  of  matter.  That  is  to  say,  the  smallest 
fragment  of  the  finest  powder  still  consists  of  a  very  large  number  of 
much  smaller  particles.  To  the  smallest  particles  which  compose 
matter  the  name  molecules  has  been  given. 

QUESTIONS. — 1.  What  is  matter  and  what  is  force?  2.  Mention  the  prin- 
cipal fundamental  properties  of  matter.  3.  Mention  the  three  states  of  aggre- 
gation. 4.  Describe  the  characteristic  properties  of  matter  in  the  solid,  liquid, 
and  gaseous  states.  5.  What  is  cohesion?  6.  Give  a  definition  of  a  crystal- 
lized substance.  7.  Under  what  circumstances  will  matter  crystallize?  8. 
State  the  difference  between  amorphous,  polymorphous,  and  isomorphous 
substances.  9.  What  is  meant  by  elasticity  or  tension  of  gases?  10.  State 
the  law  of  Mariotte. 


22  INTRODUCTION. 

Molecular  theory.  The  expression  molecule  is  derived  from  the 
Latin  word  molecula — a  little  mass,  and  means  the  smallest  particle 
of  matter  that  can  exist  by  itself,  or  into  which  matter  is  capable  of 
being  subdivided  by  physical  actions.  To  explain  more  fully  what  is 
meant  by  the  expression  molecule,  we  will  return  to  the  conversion  of 
water  into  steam. 


When  water  boils  at  the  ordinary  atmospheric  pressure  it  expands 
about  1800  times,  or  one  cubic  inch  of  water  yields  about  1800  cubic 
inches,  equal  to  about  one  cubic  foot  of  steam.  In  explaining  this 
fact  we  have  either  to  assume  that  the  water,  as  well  as  the  steam,  is 
homogeneous  matter  (Fig.  1),  or  that  the  water  consisted  of  small 
particles  of  a  given  size,  which  now  exist  in  the  steam  again  as  such, 
with  the  only  difference  that  they  are  more  widely  separated  from 
each  other  (Fig.  2). 

Of  the  many  proofs  which  we  have  of  the  fact  that  the  latter 
assumption  is  correct,  I  will  mention  but  one,  viz.,  that  the  quantities 
of  vapor  formed  by  volatile  liquids  at  any  certain  temperature  above 
the  boiling-point,  in  close  vessels  of  the  same  size,  are  the  same,  no 
matter  whether  the  vessel  was  entirely  empty  or  contains  the  vapors 
of  one,  two,  or  more  other  substances.  For  instance  :  If  we  place 
one  cubic  inch  of  water  in  a  flask  holding  one  cubic  foot,  from  which 
flask  the  air  has  been  previously  removed,  and  then  heat  the  flask  to 
the  boiling-point,  the  cubic  inch  of  water  will  evaporate,  filling  the 
vessel  with  steam.  Upon  now  introducing  into  the  flask  a  second  and 
a  third  liquid — for  instance,  alcohol  and  ether — we  find  that  of  each 
of  these  liquids  exactly  the  same  quantity  will  evaporate  which  would 


DIVISIBILITY.  23 

have  evaporated  if  these  liquids  had  been  introduced  into  the  empty 
flask.1  This  fact  is  evidence  that  there  must  be  small  particles  of 
steam  which  are  not  in  close  contact,  that  there  are  spaces  between 
these  particles  which  may  be  occupied  by  the  particles  of  a  second, 
third,  or  more  substances.  To  these  particles  of  matter  we  give  the 
name  molecules,  and  the  spaces  between  them  we  call  intermolecular 


FIG.  2. 


4 


We  have  thus  demonstrated  the  correctness,  or,  at  least,  the  likeli- 
hood of  the  so-called  molecular  theory,  but  the  proof  given  is  but  one 
of  many.  Of  these  molecules  (though  individually  by  far  too  small 
to  make  any  impression  whatever  upon  our  senses),  our  conception  is 
so  perfect  that  we  have  formed  an  idea  of  the  actual  size  of  these 
minute  particles  of  matter.  Very  good  reasons  lead  us  to  believe  that 
the  diameter  of  a  molecule  is  equal  to  about  ^o-^rio'FoT  °^  one  incn? 
and  that  one  cubic  inch  of  a  gas  under  ordinary  conditions  contains 
about  one  hundred  thousand  million  million  millions  of  molecules. 

These  figures  at  first  glance  appear  to  be  beyond  the  limit  of  human 
conception,  but  in  order  to  give  some  idea  of  the  size  of  these  mole- 
cules it  may  be  mentioned  tha/if  a  mass  of  water  as  large  as  a  pea. 
were  to  be  magnified  to  the  size_of_ojir  earth,  each  molecule  being 
magnified  in  the  same  proportion,  these  molecules  would  represent 
balls_of  about  twojnches  in  diameter.) 

Whilst  molecules  consequently  are  exceedingly  small  particles,  yet 
they  are  not  entirely  immeasurable ;  they  are,  as  Sir  W.  Thomson 

1  As  each  gas,  in  consequence  of  its  tension,  exerts  a  certain  pressure,  the  pressure  in  the 
flask  rises  with  the  introduction  of  every  additional  gas. 


24  INTRODUCTION. 

says,  pieces  of  matter  of  measurable  dimensions,  with  shape,  motion, 
and  laws  of  action,  intelligible  subjects  of  scientific  investigation. 

Before  leaving  the  molecular  theory,  I  will  mention  the  Law  (more 
correctly,  the  hypothesis)  of  Avogadro,  which  may  be  stated  as  follows  : 
All  gases  or  vapors,  without  exception,  contain,  in  the  same  volume,  the 
same  number  of  molecules,  provided  temperature  and  pressure  are  the 
same.  Or,  in  other  words  :  Equal  volumes  of  different  gases  contain, 
under  equal  circumstances,  the  same  number  of  molecules.  The  correct- 
ness of  this  law  has  good  mathematical  support  deduced  from  the  law 
of  Mariotte,  many  other  facts  and  considerations  leading  to  the  same 
assumption.  We  shall  learn,  hereafter,  that  the  law  of  Avogadro  is 
one  of  the  greatest  importance  to  the  science  of  chemistry. 

Motion  of  molecules.  Heat.  If  we  place  over  a  gas-flame  a 
vessel  containing  a  lump  of  ice  of  the  temperature  of  0°  C.,  or  32°  F., 
the  ice  gradually  melts  and  becomes  converted  into  water ;  but  if  we 
measure  with  a  thermometer  the  temperature  of  the  water  at  the 
moment  when  the  last  particle  of  ice  is  melted,  we  still  find  it  at  the 
freezing-point,  0°'C.  or  32°  F.  From  the  position  of  the  vessel  over 
the  flame,  as  well  as  from  the  fact  that  the  ice  has  been  liquefied,  we 
know  that  the  vessel  and  its  contents  have  absorbed  heat.  Yet  vessel 
and  water  show  the  same  temperature  as  before.  If  the  heat  of  the 
flame  is  allowed  to  continue  its  action  on  the  ice-cold  water,  the  ther- 
mometer will  soon  indicate  a  rapid  absorption  of  heat  until  it  reaches 
100°  C.  or  212°  F.  Then  the  water  begins  to  boil  and  escapes  in  the 
form  of  steam,  but  the  temperature  again  remains  stationary  until  the 
last  particle  of  water  has  disappeared. 

There  must  be,  consequently,  some  relation  between  the  state  of 
aggregation  of  a  substance  and  that  agent  which  we  call  heat.  It  was 
the  heat  which  liquefied  the  ice,  it  was  the  heat  which  converted  the 
liquid  water  into  steam  or  gaseous  water.  Yet  the  water,  having 
absorbed  considerable  heat  during  the  process  of  melting,  shows  a 
temperature  of  0°  C.  (32°  F.),  and  the  steam  also  having  absorbed 
large  quantities  of  heat,  shows  100°  C.  (212°  F.),  the  temperature  of 
boiling  water.  A  certain  amount  of  heat  has  consequently  been  lost 
or  at  least  hidden.  What  has  become  of  it  ? 

According  to  our  present  theory /heat  is  a  result  of  the  motion  of 
molecules\  All  molecules  of  any  substance  are  in  a  constant  vibratory 
motion,  and  the  velocity  or  amplitude  of  this  molecular  motion  deter- 
mines the  degree  of  what  we  call  heat. 

An  increase  of  heat  is  equal  to  an  increase  of  the  vibratory  motion 


DIVISIBILITY.  25 

of  the  molecules  and  a  decrease  in  temperature  is  caused  by  slower 
motion.  The  transfer  of  heat  is  a  transfer  of  the  motion  of  some 
particles  to  other  particles. 

One  of  the  effects  of  increased  heat  is  in  nearly  all  cases  an  increase 
in  volume,  or,  in  other  words,  all  substances  expand  when  heated, 
and  contract  on  cooling. 

Another  effect  of  the  application  of  heat  is,  as  we  have  just  learned, 
the  conversion  of  solids  into  liquids,  and  of  liquids  into  gases.  We 
noticed  also  the  apparent  loss  of  heat  during  this  conversion,  and  can 
easily  account  for  it  now  by  saying  that  a  certain  amount  of  vibratory 
motion  or  a  certain  velocity  of  the  molecules  (more  correctly  speaking, 
perhaps,  a  certain  amplitude  of  molecular  motion)  is  required  to  con- 
vert solids  into  liquids  and  'liquids  into  gases.  The  molecules  of 
steam  vibrate  with  a  much  greater  velocity  than  those  of  water  of  the 
same  temperature,  and  the  molecules  of  water  move  with  greater 
velocity  than  those  of  ice  of  the  same  temperature.  In  other  words, 
the  different  states  of  aggregation  depend  on  the  rapidity  of  the 
motion  of  molecules;  and  thej  heat  which  is  necessary  to  convert 
solids  into  liquids  and  liquids  into  gases,  and  which  is  not  indicated 
by  the  thermometer,  is  called  latentjieat.  j 

This  latent  heat  may  again  be  converted  into  free,  heat  (heat  capable 
of  being  indicated  by  a  thermometer),  by  reconverting  the  gasjnto  a 
liqjoidy-or  this  latter  into  a  solid.  In  both  cases  a  liberation  of  heat, 
which  is  a  transfer  of  the  motion  of  the  molecules  upon  the  surround- 
ings, will  be  noticed. 

Increase  of  volume  by  heat.  The  increase  of  volume  by  heat  is 
not  alike  for  all  matter.  Gases  expand  more  than  liquids,  liquids 
more  than  solids,  and  of  the  latter  the  metals  more  than  most  othgr 
solid  substances.  Whilst  the  expansion  of  any  two  or  more  different 
solids  or  liquids  is  not  alike,  gases  show  a  fixed  regularity  in  this 
respect,  namely,  all  gases  without  exception  expand  or  contract 
alike  when  the  temperature  is  raised  or  lowered  an  equal  number  of 
degrees. 

This  expansion  or  contraction  of  gases  is  0.3665  per  cent.,  or  -yfa  of  their 
volume  for  every  degree  centigrade ;  thus  100  volumes  of  air  become  100.3665 
volumes  when  heated  1  degree  C.,  or  136.65  when  heated  100  degrees  C.  This 
regularity  in  the  expansion  and  contraction  of  gases  is  expressed  in  the  Law  of 
Charles,  which  says :  If  the  pressure  remain  constant,  the  volume  of  a  gas  increases  \ 
regularly  as  the  temperature  increases,  and  decreases  as  the  temperature  decreases. 
If  heat  be  applied  to  a  gas  confined  in  a  closed  vessel  and  be  thus  prevented  I 


26  INTRODUCTION. 

from  expanding,  the  increase  of  heat  will  manifest  itself  as  pressure,  which 
rises  with  the  same  regularity  as  shown  for  expansion,  viz.,  0.3665  per  cent. 
for  every  degree  centigrade. 

Melting1  and  boiling-.  The  temperature  at  which  a  solid  sub- 
stance is  converted  into  a  liquid  and  this  into  a  gas,  is  of  a  certain 
fixed  degree  or  point  for  every  substance,  and  the  temperatures  at 
which  this  conversion  takes  place  are  known  as  melting-  (fusing-) 
and  boiling-points. 

Some  forms  of  matter  appear  incapable  of  existing  in  the  three 
states  of  aggregation,  like  water.  As  yet,  we  know  carbon  in  the 
solid  state  only,  and  the  conversion  of  some  gases,  as,  for  instance, 
oxygen  and  hydrogen,  into  liquids  or  solids,  has  been  accomplished 
only  recently  and  in  small  quantities. 

Other  substances,  again,  may  assume  two,  but  not  the  third  state. 
Some  substances  pass  from  -the  solid  directly  into  the  gaseous  state 
(ammonium  chloride,  calomel),  and  the  process  of  converting  a  solid 
into  a  gas  directly,  and  this  back  again  into  a  solid,  is  called  sublima- 
tion. 

(Distillation  is  the  conversion  of  a  liquid  into  a  gas,  and  the  recon- 
densation  of  the  gas  into  a  liquid. 


Many  liquids,  and  even  some  solids,  evaporate  or  assume  the  gaseous  state  at 
nearly  all  temperatures.  Water  and  ice,  mercury,  camphor,  and  many  other 
substances  vaporize  at  temperatures  which  are  far  below  their  regular  boiling- 
points.  This  fact  is  to  be  explained  by  the  assumption  that  during  the  rapid 
vibratory  motion  of  the  particles  of  these  masses,  some  particles  are  driven 
from  the  surface  beyond  the  sphere  to  which  the  surrounding  molecules  exert 
an  attraction,  and  thus  intermingle  with  the  molecules  of  the  surrounding  air. 

This  evaporation,  which  takes  place  at  various  temperatures  and  at  the 
surface  only,  is  not  to  be  confounded  with  boiling,  which  is  the  rapid  conver- 
sion of  a  liquid  into  a  gas  at  a  fixed  temperature  with  the  phenomena  of  ebulli- 
tion, due  to  the  formation  of  gas  in  the  mass  of  liquid.  Bojling-point  may 
therefore  be  denned  as  the  highest  point  to  which  any  liquid  nan  baJieated 
under  the  normal  pressure  of  one  atmosphere. 

Thermometers  are  instruments  indicating  different  temperatures. 
Use  is  made  in  their  construction  of  the  change  in  volume  of  dif- 
ferent substances  by  the  action  of  heat.  The  most  common  ther- 
mometer is  the  mercury  thermometer.  This  instrument  may  be 
easily  constructed  by  partly  filling  with  mercury  a  glass  tube  having 
a  bulb  at  the  lower  end,  and  placing  it  into  boiling  water.  The 
point  to  which  the  mercury  rises  is  marked  B.  P.  (boiling-point), 
and  the  tube  sealed  by  fusion  of  the  glass.  It  is  then  placed  in 


DIVISIBILITY. 


27 


FIG.  3. 


100 


212° 


melting  ice,  and  the  point  to  which  the  mercury  sinks  is  marked  F.  P. 
(freezing-point).     The  distance  between  the  boiling-  and  freezing- 
points  is  then  divided  into  100  degrees  in  the  so-called  centigrade 
thermometer,   or   into    180   degrees   in  the 
Fahrenheit  thermometer.     The  inventor  of 
the    latter    instrument,    Fahrenheit,    com- 
menced counting   not    from    the   freezing- 
point,  but  32°  below  it,  which  causes  the 
freezing-point   to   be  at  32°,   the  boiling- 
point  at  180°  above,  it,  or  at  212°.    (Fig.  3.) 

Molecular  motion.  Heat  is  but  one  of 
the  results  of  molecular  motioijL ;  other  results 
are  light,  actinism,  electricity,  and  magnjet- 
igjn. 

When  a  body  is  heated  the  molecules  vibrate 
quicker,  and  this  molecular  motion  gives  rise  to 
heat  waves  in  the  assumed  surrounding  and  all- 
pervading  medium  called  ether;  if  the  heating  be 
continued  to  a  higher  degree,  the  body  begins  to 
give  out  light,  which  is  due  to  ether  waves  of 
shorter  length ;  and  if  heated  yet  higher,  it  gives 
out  not  only  dark  heat  waves  and  light  waves,  but 
also  waves  of  still  shorter  length,  which  make 
no  direct  impression  on  our  senses,  but  which  are 
capable  of  producing  chemical  changes  in  certain 
substances,  and  are  known  as  actinic  waves.  Of 
the  character  of  the  molecular  motion  causing 
electricity  and  magnetism  we  know  little,  and 
the  various  theories  which  have  been  advanced 

in  order  to  explain  electrical  phenomena  are  inadequate  and  insufficient  to  do 
go  satisfactorily. 

Specific  heat.  Equal  weights  of  different  substances  require  dif- 
ferent quantities  of  heat  to  raise  them  to  the  same  temperature.  For 
instance :  The  same  quantity  of  heat  which  is  sufficient  to  raise  one 
pound  of  water  from  60°  to  70°  will  raise  the  temperature  of  one 
pound  of  olive  oil  from  60°  to  80°,  or  two  pounds  of  olive  oil  from 
60°  to  70°.  Olive  oil  consequently  requires  only  one-half  of  the  heat 
necessary  to  raise  an  equal  weight  of  water  the  same  number  of 
degrees,  {f  Specific  heat  is  therefore  the  heat  required  to  raise  a  certain 
weight  of  a  substance  a  certain  number  of  degrees,  compared  with^C 
the  heat  required  to  raise  an  equal  weight  of  water  the  same  number 
of  degrees.  | 


Centigrade.      Fahrenheit. 
Thermometric  scales. 


28  INTRODUCTION. 

The  heat  required  to  raise  one  pound  of  water  one  degree  centi- 
grade is  usually  taken  as  the  unit  of  comparison.  On  thus  comparing 
olive  oil,  we  find  its  specific  heat  to  be  J.  If  we  say  the  specific 
heat  of  mercury  is  -^  we  indicate  that  equal  quantities  of  heat  will 
be  required  to  raise  one  pound  of  water  or  32  pounds  of  mercury  one 
degree,  or  that  the  heat  which  raises  one  pound  of  water  one  degree 
will  raise  One  pound  of  mercury  32  degrees. 


3.  GRAVITATION. 

Action  of  gravitation.  Every  particle  of  matter  in  the  universe 
attracts  every  other  particle;  consequently,  all  masses  attract  each 
other,  and  this  attraction  is  known  as  gravitation.  The  action  of 
gravitation  between  the  thousands  of  heavenly  bodies  moving  in  the 
universe  is  to  be  considered  by  astronomy,  but  some  of  the  phenomena 
caused  by  the  mutual  attraction  of  the  substances  composing  the  earth 
are  of  importance  for  our  present  consideration. 

Such  phenomena  caused  by  gravitation  are  the  falling  of  substances, 
the  flowing  of  rivers,  the  resistance  which  a  substance  offers  on  being 
lifted  or  carried.  A  body  thrown  up  into  the  air  or  deprived  of  its 
support  will  fall  back  upon  the  earth.  In  this  case  the  mutual  attrac- 
tion between  the  earth  and  the  substance  has  caused  its  fall.  It 
might  appear  that  in  this  case  the  attraction  was  not  mutual,  but  ex- 
erted by  the  earth  only;  it  has  been  proved,  however,  by  most  exact 
experiments,  that  there  is  also  an  attraction  of  the  falling  substance 
for  the  earth,  but  the  amount  of  the  force  of  this  attraction  is  directly 
proportional  to  the  mass  of  the  bodies,  and  consequently  .too  insig- 
jrificant  in  the  above  case  to  be  noticed. 

The  law  of  gravitation,  known  as  N^toT^slaw,  may  thus  be  stated : 
/  All  bodies  attract  each  other  with  a  force  directly  proportional  to 
I  their  masses  and  inversely  proportional  to  the  squares  of  their  distance 
\  apart. 

QUESTIONS. — 11.  What  two  kinds  of  divisibility  of  matter  do  we  distinguish, 
and  by  what  actions  are  they  accomplished  ?  12.  Explain  the  term  molecule. 
13.  Mention  one  of  the  facts  which  prove  that  a  gas  consists  of  particles  with 
intervals  between  them.  14.  State  the  law  of  Avogadro.  15.  Mention  the 
effects  produced  by  increased  velocity  of  the  molecules  of  a  mass.  16.  Give  an 
explanation  of  the  expressions— latent  heat,  free  heat,  and  specific  heat.  17. 
Explain  the  construction  of  a  mercury  thermometer.  18.  How  many  degrees 
of  Fahrenheit  are  equal  to  50°  C.  ?  19.  How  many  degrees  of  centigrade  are 
equal  to  167°  F.  ?  20.  What  is  distillation,  and  what  is  sublimation  ? 


GRAVITATION.  29 

Weight  is  an  expression  used  to  denote  the  quantity  of  mutual 
attraction  between  the  earth  and  the  body  weighed.  Here  again,  the 
attraction  of  the  substance  for  the  earth  is  not  taken  into  considera- 
tion. All  our  weighing  is  a  comparison  with,  or  measurement  by, 
some  standard  weight,  such  as  pound,  ounce,  gramme,  etc. 

Specific  weight  or  specific  gravity  denotes  the  weight  of  a  body, 
as  compared  with  the  weight  of  an  equal  bulk  or  equal  volume  of 
another  substance,  which  is  taken  as  a  standard  or  unit.  The  word 
density  is  frequently  used  for  specific  weight,  as  density  means 
comparative  mass.  By  the  density  of  a  body  consequently  is  meant 
its  mass  (or  quantity  of  matter)  compared  with  the  mass  of  an  equal 
volume  of  some  body  arbitrarily  chosen  as  a  standard.  The  standard 
or  unit  adopted  for  all  solids  and  liquids,  if  not  otherwise  stated,  is 
water  at  a  temperature  of  15°  C.  =  59°  F. 

Specific  weight  is  generally  expressed  in  numbers  which  denote  how 
many  times  the  weight  of  an  equal  bulk  of  water  is  contained  in  the 
weight  of  the  substance  in  question.  If  we  say  that  mercury  has  a 
specific  gravity  or  density  of  13.6,  or  that  alcohol  has  a  specific  gravity 
of  0.79,  we  mean  that  equal  volumes  of  water,  mercury,  and  alcohol 
represent  weights  in  the  proportion  of  1, 13.6,  and  0.79,  or  100, 1360, 
and  79. 

The  standard  or  unit  chosen  for  comparing  the  specific  gravity  of 
gases  is  either  atmospheric  air  or  hydrogen. 

In  order  to  obtain  the  specific  gravity  of  any  liquid,  it  is  only 
necessary  to  weigh  equal  volumes  of  water  and  the  liquid  to  be  ex- 
amined, and  then  to  divide  the  weight  of  the  liquid  by  the  weight  of 
the  water. 

A  second  method  by  which  the  specific  gravity  of  liquids  may  be 
determined  is  by  means  of  the  instruments  known  as  hydrometers,  or, 
if  made  for  some  special  purposes,  as  alcoholometers,  urinometers, 
alkalimeters,  lactometers,  etc. 

Hydrometers  are  instruments  generally  made  of  glass  tubes, 
having  a  weight  at  the  lower  end  to  maintain  them  in  an  upright 
position  in  the  fluid  to  be  tested  as  to  specific  gravity,  and  a  stem 
above,  bearing  a  scale.  /The  principle  upon  which  their  construction 
depends  is  the  fact  thaisa  solid  substance  when  placed  in  a  liquid 
heavier  than  itself  displaces  a  volume  of  this  liquid  equal  to  the 
whole__weight  of  the  displacing  substance^  The  hydrometer  will 
consequently  sink  lower  in  liquids  of  lower  specific  gravity  than  in 


30  INTRODUCTION. 

heavier  ones,  as  the  instrument  has  to  displace  a  larger  bulk  of  liquid 
in  the  lighter  than  in  the  heavier  liquid  in  order  to  displace  its  own 
weight. 

"Weight  of  gases.  We  have  so  far  considered  the  gravity  of  solids 
and  liquids  only,  and  the  next  question  will  be :  Do  gases  also  possess 
weight — are  they  also  attracted  by  the  earth  ?  The  fact  that  a  gas, 
when  generated  or  liberated,  expands  in  every  direction,  might  indi- 
cate that  the  molecules  of  a  gas  have  no  weight,  are  not  attracted  by 
the  earth.  A  few  simple  experiments  will,  however,  show  that  gases, 
like  all  other  substances,  have  weight.  Thus  a  flask  from  which  the 
atmospheric  air  has  been  removed  will  weigh  less  than  the  same  flask 
when  filled  with  atmospheric  air  or  any  other  gas. 

Barometer.  A  second  method  by  which  may  be  demonstrated 
the  fact  that  atmospheric  air  possesses  weight,  is  by  means  of  the 
barometer.  The  atmosphere  is  that  ocean  of  gas  which  encircles  the 
earth  with  a  layer  some  50  or  100  miles  in  thickness,  exerting  a  con- 
siderable pressure  upon  all  substances  by  its  weight.  The  instru- 
ments used  for  measuring  that  pressure  are  known  as  barometers,  and 
the  most  common  form  of  these  is  the  mercury  barometer.  It  may 
be  constructed  by  filling  with  mercury  a  glass  tube  closed  at  one  end 
(and  about  three  feet  long)  and  then  inverting  it  in  a  vessel  contain- 
ing mercury,  when  it  will  be  found  that  the  mercury  no  longer  fills 
the  tube  to  the  top,  but  only  to  a  height  of  about  30  inches,  leaving 
a  vacuum  above.  The  column  of  mercury  is  maintained  at  this 
height  by  the  pressure  of  the  atmosphere  upon  the  surface  of  the 
mercury  in  the  vessel ;  a  column  of  mercury  about  30  inches  high 
must  consequently  exert  a  pressure  equal  to  the  pressure  of  a  column 
of  the  atmosphere  of  the  same  diameter  as  that  of  the  mercury 
column. 

As  the  weight  of  a  column  of  mercury,  having  a  base  of  one  square 
inch  and  a  height  of  about  30  inches,  is  equal  to  about  15  pounds,  a 
column  of  atmosphere  having  also  a  base  of  one  square  inch  must  also 
weigh  15  pounds.  In  other  words,  the  atmospheric jpressure js  equal 
to  about  JJ)  pounds  to  the  square  inch,  or  about  one  ton  to  the  square 
foot.  This  enormous  pressure  is  borne  without  inconvenience  by  the 
animal  frame  in  consequence  of  the  perfect  uniformity  of  the  pressure 
in  every  direction. 

A  barometer  may  be  constructed  of  other  liquids  than  mercury,  but  as  the 
height  of  the  column  must  always  bear  an  inverse  proportion  to  the  density  of 


GRAVITATION.  31 

the  liquid  used,  the  length  of  the  tube  required  must  be  greater  for  lighter 
liquids.  As  water  is  13.6  times  lighter  than  mercury,  the  height  of  a  water 
column  to  balance  the  atmospheric  pressure  is  13.6  times  30  inches,  or  about  34 
feet,  which  would  therefore  be  the  height  of  the  column  of  water  required. 

Changes  in  the  atmospheric  pressure.  The  height  of  the  mer- 
cury column  in  a  barometer  is  not  the  same  at  all  times,  but  varies 
within  certain  limits.  These  variations  are  due  to  a  number  of  causes 
disturbing  the  density  of  the  atmosphere,  and  are  chiefly  atmospheric 
currents,  temperature,  and  the  amount  of  moisture  contained  in  the 
atmosphere. 

As  the  height  and  with  it  the  density  of  the  atmosphere  diminishes 
gradually  from  the  level  of  the  sea  upward,  the  height  of  the  mercury 
column  will  be  lower  in  localities  situated  at  an  elevation.  This 
diminution  of  pressure  is  so  constant  that  the  barometer  is  used  for 
estimating  elevations. 

Influence  of  pressure  on  state  of  aggregation.  We  have  seen 
that  the  volume  of  a  substance,  and,  more  especially,  of  a  gas,  depends 
upon  pressure  and  temperature,  an  increase  of  pressure  or  decrease  of 
temperature  causing  the  volume  to  become  smaller.  We  learned  also 
that  liquids  may  be  converted  into  gases,  and  that  this  conversion ' 
takes  place  at  a  certain  fixed  temperature  called  the  boiling-point. 
This  point,  however,  changes  with  the  pressure.  An  increased  pres- 
sure will  raise,  a  decreased  pressure  will  lower,  the  boiling-point. 

Thus  water  boils  at  the  normal  pressure  of  one  atmosphere  at  100°  0.  (212° 
F.),  but  it  will  boil  at  a  lower  temperature  on  mountains  in  consequence  of  the 
diminished  atmospheric  pressure.  If  the  pressure  be  increased,  as,  for  instance, 
in  steam-boilers,  the  boiling-point  will  be  raised.  Thus  the  boiling-point  of 
water  under  a  pressure  of  two  atmospheres  is  at  122°  C.  (251°  F.),  of  five  atmos- 
pheres at  153°  C.  (307°  F.),  of  ten  atmospheres  at  180°  C.  (356°  F.) 

QUESTIONS.— 21.  What  is  gravitation?  22.  Mention  some  phenomena 
caused  by  gravitation  ?  23.  Give  a  definition  of  weight.  24.  What  is  specific 
weight  ?  25.  Name  the  substances  adopted  as  standards  for  the  determination 
of  specific  gravities  of  solids,  liquids,  and  gases.  36.  What  is  the  use  made  of 
hydrometers,  and  on  what  principle  is  their  construction  based?  27.  Explain 
construction  and  use  of  the  mercury  barometer.  28.  Mention  some  of  the 
causes  which  have  an  influence  upon  the  height  of  the  mercury  column  in 
the  barometer.  29.  What  is  the  atmospheric  pressure  upon  a  surface  of  five 
square  feet?  30.  State  the  relation  between  boiling-point,  temperature,  and 
pressure. 


32  INTRODUCTION. 

4.    POROSITY. 

Nature  of  porosity.  We  have  seen  that  the  molecules  of  any  sub- 
stance are  not  in  absolute  contact,  but  that  there  are  spaces  between 
them  which  we  call  intermolecular  spaces ;  the  property  of  matter  to 
have  spaces  between  the  particles  composing  it  is  known  as  porosity. 

In  the  case  of  solids,  these  spaces  or  pores  are  sometimes  of  con- 
siderable size,  visible  even  to  the  naked  eye,  as,  for  instance,  in 
charcoal,  whilst  in  most  cases  they  cannot  be  discovered,  even  by  the 
microscope.  That  even  apparently  very  dense  substances  are  porous, 
can  be  demonstrated  by  the  fact  that  liquids  may  be  pressed  through 
metallic  disks  of  considerable  thickness,  that  gases  may  be  caused  to 
pass  through  plates  of  metal  or  stone^that  solids  dissolve  in  liquids 
without  showing  a  corresponding  increase  in  volume  of  the  solution 
thus  obtained,  and,  finally,  also  by  the  fact  that  substances  suffer  ex- 
pansion or  contraction  in  consequence  of  increased  or  diminished 
heat,  or  in  consequence  of  mechanical  pressure. 

Surface.  In  every-day  life  the  expression  "surface"  refers  to  that 
part  of  a  substance  which  is  open  to  our  senses,  visible  and  measur- 
able ;  but  from  a  more  scientific  point  of  view,  we  have  also  to  take 
into  consideration  those  surfaces  which,  inconsequence  of  porosity, 
extend  to  the  interior  of  matter  and  are  invisible  to  our  eyes  and 
absolutely  immeasurable  by  instruments. 

Surface-action.  Attraction  acts  differently  under  different  condi- 
tions, and,  accordingly,  we  assign  different  names  to  it.  We  call  it 
cohesion  when  it  acts  between  molecules,  gravitation  when  acting 
between  masses,  and  surface-action  or  surface-attraction  when  the 
attraction  is  exerted  either  by  the  visible  surface  or  by  that  surface 
which  pervades  the  whole  interior  of  matter.  The  phenomena  caused 
by  this  surface- action  are  extremely  manifold,  and  some  are  of  suffi- 
cient interest  to  be  taken  into  consideration. 

Adhesion.  Most  solid  substances,  when  immersed  in  water, 
alcohol,  or  many  other  liquids,  become  moist ;  immersed  in  mercury, 
they  remain  dry.  We  explain  this  fact  by  saying  that  the  surfaces 
of  most  solid  substances  exert  an  attraction  for  the  particles  of  such 
liquids  as  water  and  alcohol  to  such  an  extent  that  these  particles 
adhere  to  the  surface  of  the  solids.  Such  an  attraction,  however, 
does  not  manifest  itself  for  the  particles  of  mercury.  This  form  of 


POROSITY.  33 

surface-attraction  by  which  liquids  are  caused  to  adhere  to  solids  is 
\  called  adhesion^ 

This  adhesion  may  be  noticed  also  between  two  plates  having  plane 
surfaces.  A  drop  of  water  pressed  between  these  plates  will  cause 
them  to  adhere  to  each  other.  The  application  and  use  of  glue  and 
mucilage,  our  methods  of  writing  and  painting,  the  welding  together 
of  pieces  of  metal,  etc.,  depend  on  this  kind  of  surface-action. 

Capillary  attraction.  Whilst  it  is  the  general  rule  that  liquids 
in  vessels  present  a  horizontal  surface,  this  rule  does  not  hold  good 
near  the  sides  of  the  vessel.  When  the  liquids  wet  the  vessel,  as  in 
the  case  of  water  in  a  glass  vessel,  the  surface  is  somewhat  concave 
in  consequence  of  the  attraction  of  the  glass  surface  for  the  particles 
of  water ;  on  the  contrary,  when  the  liquids  do  not  wet  the  vessel,  as 
in  the  case  of  mercury  in  a  glass  vessel,  the  surface  is  somewhat 
convex.  The  smaller  the  diameter  of  the  vessel  holding  the  liquids, 
the  more  concave  or  convex  will  the  surface  be.  If  a  narrow  tube  is 
placed  in  a  liquid,  this  surface-action  will  be  more  striking,  and  it 
will  be  found  that  a  liquid  wetting  the  tube  will  not  only  have  a 
completely  concave  surface,  but  the  level  of  the  liquid  stands  per- 
ceptibly higher  in  the  tube  than  the  level  of  the  liquid  outside. 
Substances  not  wetting  the  tube  will  show  the  reverse  action,  namely, 
the  surface  inside  of  the  tube  will  be  convex,  and  will  be  below  the 
level  of  the  liquid  outside. 

The  attraction  of  the  surface  of  tubes  for  liquids,  manifesting 
itself  in  the  concave  shape  of  the  surface  and  in  the  elevation  of  the 
liquid  near  the  tube,  is  known  as  capillary  attraction.  Capillary 
elevations  and  depressions  depend  upon  the  diameter  of  the  tube, 
temperature,  and  the  nature  of  the  liquid.  The  narrower  the  tube, 
the  higher  the  elevation  or  the  lower  the  depression ;  both  are 
diminished  by  increased  temperature.  /Capillary  elevations  and 
depressions,  all  other  circumstances  being  equal,  are  inversely  pro- 
portional to  the  diameters  of  the  tubes.) 

Defining  the  phenomena  of  capillary  attraction  more  scientifically, 
we  may  say  that  the  adhesive  force  of  glass,  wood,  etc.,  for  water  and 
most  other  liquids  exceeds  the  cohesive  force  acting  between  the 
molecules  of  these  liquids,  while  in  mercury  the  cohesive  force  pre- 
dominates over  the  adhesive. 

Surface-attraction  of  solids  for  gases.  Any  dry  solid  sub- 
stance, carefully  weighed,  will,  after  having  been  exposed  to  a  higher 

3 


34  INTRODUCTION. 

temperature,  show  a  decrease  in  weight  whilst  yet  warm.  Upon 
cooling,  the  original  weight  will  be  restored.  This  fact  cannot  be 
explained  otherwise  than  that  some  substance  or  substances  must 
have  been  expelled  by  heat,  and  that  this  substance  or  these  sub- 
stances are  reabsorbed  on  cooling. 

This  is  actually  the  case,  and  the  substances  expelled  and  reab- 
sorbed are  the  gaseous  constituents  of  the  atmospheric  air,  chiefly  the 
aqueous  vapor. 

Every  solid  substance  upon  our  earth  condenses  upon  its  surface 
more  or  less  of  the  gaseous  constituents  of  the  atmosphere.  This 
condensation  takes  place  upon  the  outer  as  well  as  upon  the  inner 
surface.  The  amount  of  gas  absorbed  depends  upon  the  nature  of 
the  gas  as  well  as  upon  the  nature  of  the  absorbing  solid.  Some  of 
the  so-called  porous  substances,  such  as  charcoal,  generally  condense 
or  absorb  larger  quantities  than  solids  of  a  more  dense  and  compact 
structure.  Heat,  as  stated  above,  counteracts  this  absorbing  power. 

Surface-attraction  of  solids  for  liquids  or  for  solids  held  in 
solution.  When  a  mixture  of  different  liquids,  or  a  mixture  of 
different  solids  dissolved  in  a  liquid,  is  brought  in  contact  with  or 
filtered  through  a  porous  solid  substance,  such  as  charcoal  or  bone- 
black,  it  will  be  found  that  the  surface  of  the  solid  substance  retains 
a  certain  amount  of  the  liquids  or  of  the  solids  held  in  solution,  and 
that  it  retains  more  of  one  kind  than  of  another. 

It  is  this  peculiarity  of  surface-attraction  which  is  made  use  of  in 
purifying  drinking-water  by  allowing  it  to  pass  through  charcoal. 
Bone-black  is  similarly  used  for  decolorizing  sugar-syrup  and  other 
liquids. 

Absorbing-  power  of  liquids.  In  a  similar  manner  as  in  the 
case  of  solids,  liquids  also  exert  an  attraction  for  gases^  When  a 
gas  is  condensed  within  the  pores  or  upon  the  surface  of  a  solid,  or 
when  it  is  taken  up  and  condensed  by  a  liquid,  we  call  the  process 
absorption^}  This  absorbing  power  of  different  liquids  for  different 
gases  varie^  greatly ;  it  is  facilitated  by  low  temperature  and  high 
pressure,  and  counteracted  by  high  temperature  and  removal  of 
pressure.  Thus  :  One  volume  of  water  absorbs  at  ordinary  tempera- 
ture and  pressure  about  0.03  volume  of  oxygen,  1  volume  of  carbon 
dioxide,  30  volumes  of  sulphur  dioxide,  and  800  volumes  of  ammonia. 

Diffusion.  When  a  cylindrical  glass  vessel  has  been  partially 
filled  with  water,  and  alcohol,  which  is  specifically  lighter  than 


POROSITY.  35 

water,  is  poured  upon  it,  care  being  taken  to  prevent  a  mixing  of  the 
two  liquids,  so  as  to  form  two  distinct  layers,  it  will  be  found  that 
after  a  certain  lapse  of  time  the  two  liquids  have  mixed  with  each 
other,  particles  of  water  having  entered  the  alcohol  and  particles  of 
alcohol  the  water,  until  a  uniform  mixture  of  the  two  liquids  has 
taken  place.  Upon  repeating  the  experiment  with  a  layer  of  water 
over  a  column  of  solution  of  common  salt,  it  will  again  be  found  that 
the  two  liquids  gradually  enter  one  into  the  other  until  a  uniform 
salt  solution  has  been  formed. 

In  a  similar  manner,  two  or  more  gases  introduced  into  a  vessel  or 
a  room  will  readily  mix  with  each  other.  /This  gradual  passage  of 
one  liquid  into  another,  of  a  dissolved  substance  into  another  liquid, 
or  of  one  gas  into  another  gas,  ^is  called  diffusion^ 

Osmose.  Dialysis.  This  diffusion  takes  place  also  when  two 
liquids  are  separated  by  a  porous  diaphragm,  such  as  bladder  or 
parchment  paper,  and  it  is  then  called  osmose  or  dialysis. 

The  apparatus  used  for  dialysis  is  called  a  dialyzer  (Fig.  4),  and 
consists  usually  of  a  glass  cylinder,  open  at  one  end  and  closed  at  the 
other  by  the  membrane  to  be  used  as  the  separating  medium.     This 
vessel  is  placed  into  another,  and 
the  two  liquids  are  introduced  into 
the   two   vessels.     If  the   inner 
vessel  be  filled  Avith  a  salt  solution 
and  the  outer  one  with  pure  water, 
it  will  be  found  that  part  of  the 
salt  solution  passes  through  the 
membrane  into  the  water,  whilst 
at  the   same   time  water  passes 
over  to  the  salt  solution. 

On  subjecting  different  sub- 
stances to  this  process  of  dialysis,  it  has  been  found  that  some  sub- 
stances pass  through  the  membrane  with  much  greater  facility  or  in 
larger  quantities  than  others,  and  that  some  do  not  pass  through  at 
all.  As  a  general  rule,  crystallizable  substances  pass  through  more 
freely  than  amorphous  substances.  /Those  substances  which  do  not 
pass  through  membranes  in  the  process  of  dialysis  are  known  as  col- 
loids, those  which  diffuse  rapidly  crystalloids.\ 

Capillary  attraction,  or,  more  generally  speaking,  surface-attraction, 
is  undoubtedly  to  some  extent  the  cause  of  the  phenomena  of  osmose, 
the  surface  of  the  diaphragm  exercising  an  attraction  upon  the  liquids. 


36  INTRODUCTION. 

Diffusion  of  gases.  A  diffusion  similar  to  that  of  liquids  takes 
place  also  when  two  different  gases  are  separated  from  each  other  by 
some  porous  substance,  such  as  burned  clay,  gypsum,  and  others. 

It  has  been  found  that  specifically  lighter  gases  diffuse  with  greater 
rapidity  than  the  heavier  ones.  The  quantities  of  two  different  gases 
which  diffuse  into  one  another  in  a  given  time  are,  as  a  general  rule, 
inversely  as  the  square  roots  of  their  specific  gravities.  Oxygen  is 
sixteen  times  as  heavy  as  hydrogen ;  when  the  two  gases  diffuse,  it 
will  be  found  that  four  times  as  much  hydrogen  has  penetrated  into 
the  oxygen  as  of  the  latter  gas  into  the  hydrogen.  This  regularity 
in  the  diffusion  of  gases  is  expressed  in  the  Law  of  Graham,  thus : 
'The  velocity  of  the  diffusion  of  any  gas  is  inversely  proportional  to 
the  square  root  of  its  density. 

Indestructibility.  All  matter  is  indestructible — i.  e.,  cannot  pos- 
sibly be  destroyed  by  any  means  whatever,  and  this  property  is  known 
as  indestructibility.  Form,  shape,  appearance,  properties,  etc.,  of 
matter  may  be  changed  in  many  different  ways,  but  the  matter  itself 
can  never  be  annihilated.  Apparently,  matter  often  disappears,  as, 
for  instance,  when  water  evaporates  or  oil  burns;  but  these  apparent 
destructions  indicate  simply  a  change  in  the  form  of  matter;  in  both 
cases  gases  are  formed,  which  become  invisible  constituents  of  the 
atmospheric  air,  and  can,  therefore,  not  be  seen  for  the  time  being, 
but  may  be  recondensed  or  rendered  visible  in  various  ways. 

Not  only  is  matter  indestructible,  energy  also  partakes  of  this 
property.  Energy  may  be  converted  from  one  form  into  some  other 
form.  Motion  may  be  converted  into  heat,  and  heat  into  motion,  or 
this  motion  into  electrical  energy  and  chemical  energy.  In  fact,  all 
the  different  forms  of  energy  are  convertible  one  into  the  other  with- 
out loss.  This  fact  is  spoken  of  as  the  Law  of  the  conservation  of 
energy. 

To  repeat :  The  total  quantity  of  matter  in  the  universe  is  con- 
stant, and  the  same  is  true  of  energy. 

QUESTIONS. — 31.  What  is  porosity  ?  32.  What  two  meanings  may  be  assigned 
to  the  word  surface  ?  33.  Mention  some  phenomena  caused  by  surface-action. 
34.  Explain  the  term  adhesion.  35.  Under  what  circumstances  can  capillary 
attraction  be  noticed,  and  how  does  it  manifest  itself?  36.  Give  an  explana- 
tion of  the  word  absorption,  and  mention  some  instances  of  the  absorption  of 
gases  by  solids  or  liquids.  37.  What  do  we  understand  by  diffusion  of  gases 
or  liquids  ?  38.  Define  the  word  osmose.  39.  Which  substances  are  most  apt 
to  dialyze,  and  which  have  no  such  tendency  ?  40.  What  is  meant  by  saying 
that  matter  and  energy  are  indestructible? 


II. 

PRINCIPLES  OF  CHEMISTRY. 

RESULTS  OF  THE  ATTRACTION  BETWEEN  ATOMS, 


5.    CHEMICAL  DIVISIBILITY. 

Decomposition  by  heat.  The  results  of  the  action  of  heat  upon 
matter  have  been  stated  to  be :  Increased  velocity  of  the  motion  of 
molecules,  increase  in  volume  of  the  substance  heated,  and  in  many 
cases  a  conversion  of  solids  into  liquids  and  of  these  into  gases.  Be- 
sides these  results  there  frequently  may  be  noticed  another,  now  to  be 
mentioned. 

FIG.  5. 


Decomposition  of  mercuric  oxide  in  A  ;  collection  of  mercury  in  B,  and  of  oxygen  in  C. 

To  illustrate  this  action  of  heat,  we  will  select  the  red  oxide  of 
mercury,  a  solid  substance  which  is  insoluble  in  water,  almost  taste- 
less, and  of  a  brick-red  color.  When  this  oxide  of  mercury  is  placed 
in  a  glass  tube  and  heated,  it  will  be  found  to  disappear  gradually, 
and  we  might  assume  that  it  has  been  converted  into  a  gas  from 
which,  upon  cooling,  the  red  oxide  of  mercury  would  be  re-obtained. 
If  the  apparatus  for  heating  the  oxide  of  mercury  be  so  constructed 
that  the  escaping  gases  may  be  collected  and  cooled,  we  shall  not  find 
the  red  oxide  in  our  receiver,  but  in  its  place  a  colorless  gas,  whilst  at 

(87> 


38  PRINCIPLES  OF  CHEMISTS  Y. 

the  same  time  globules  of  metallic  mercury  will  be  found  deposited 
in  the  cooler  parts  of  the  apparatus  (Fig.  5). 

The  action  of  heat  consequently  has  in  this  case  produced  an  effect 
entirely  different  from  the  effects  spoken  of  heretofore.  There  is  no 
doubt  that  the  first  action  of  the  heat  upon  the  oxide  of  mercury  is 
an  increased  velocity  of  the  motion  of  its  molecules  and  simulta- 
neously an  increase  of  its  volume,  but  afterward  a  decomposition  of 
the  oxide  takes  place,  and  two  substances  are  liberated,  each  different 
from  the  oxide. 

One  of  these  substances  is  a  silvery-white,  heavy,  liquid  metal,  the 
mercury ;  the  other  substance  is  a  colorless,  odorless  gas,  which  sup- 
ports combustion  much  more  freely  than  does  atmospheric  air,  and  is 
known  as  oxygen. 

Elements.  We  have  thus  succeeded  in  proving  that  red  oxide  of 
mercury  may  be  converted  or  decomposed  by  the  mere  action  of  heat 
into  mercury  and  oxygen.  It  is  but  natural  to  inquire  whether  it 
would  be  possible  further  to  subdivide  the  mercury  or  the  oxygen 
into  two  or  more  new  substances  of  different  properties.  To  this 
question,  which  has  been  experimentally  propounded  to  Nature  over 
and  over  again,  we  have  but  one  answer,  viz. :  Oxygen  and  mercury 
are  substances  incapable  of  decomposition  by  any  method  or  means 
as  yet  known  to  us.  They  resist  the  powerful  influences  of  electricity 
and  heat,  even  when  raised  to  the  highest  attainable  degrees  of  in- 
tensity, and  they  issue  -unchanged  from  every  variety  of  reaction 
hitherto  devised  with  the  view  of  resolving  them  into  simpler  forms 
of  matter. 

Therefore  we  are  justified  in  regarding  oxygen  and  mercury  as  non- 
decomposable  or  simple  substances,  in  contradistinction  to  compound 
or  decomposable  substances,  such  as  the  red  pxide  of  mercury. 

All  substances  which  cannot  by  any  known  means  be  resolved  into 
impler  forms  of  matter,  are  called  elements  A  (all  substances  which 
may,  by  one  process  or  another,  be  subdivided  or-decomposed  in  such 
a  manner  that  new  substances  with  new  properties  are  formed,  are 
called  compound  substances  or  compounds.  \ 

While  the  number  of  known  compounds  exceeds  many  thousands, 
the  number  of  elements  is  comparatively  small,  but  sixty-seven  of 
these  simple  substances  being  known  to  exist  on  our  earth.  And  yet 
this  small  number  of  elements,  by  combining  with  each  other  in  many 
different  proportions,  form  all  that  boundless  variety  of  matter  which 
we  see  in  nature. 


CHEMICAL  DIVISIBILITY.  39 

Chemical  affinity.  There  must  be  some  cause  which  enables  or 
even  forces  the  different  elements  to  unite  with  each  other  so  as  to 
Form  compound  bodies.  There  must  be,  for  instance,  a  cause  which 
enables  oxygen  and  mercury  to  combine  and  form  a  red  powder. 

This  cause  is  to  be  found  in  the  existence  of  another  form  of  the 
general  attraction  which  causes  the  smallest  particles  of  different 
elements  to  unite  to  form  new  substances  with  new  properties.  This 
kind  of  attractive  power  is  called  chemical  force  or  chemical  affinity, 
and  bodies  possessing  this  capacity  of  uniting  with  each  other  are  said 
to  have  an  affinity  for  each  other. 

Thore  is  a  great  difference  between  chemical  attraction  and  the 
various  forms  of  attraction  spoken  of  heretofore.  Cohesion  simply 
holds  together  the  molecules*  of  the  same  substance,  adhesion_acts 
chiefly  between  the  molecules  of  solid  and  liquid  substances,  gravita- 
tion acts  between  masses.  But  all  these  forces  do  not  change  the 
nature,  the  external  and  internal  properties  of  matter ;  this  is  done 
when  chemical  force  or  affinity  is  operating,  when  a  chemical  change 
takes  place. 

For  instance  :  In  a  piece  of  yellow  sulphur  the  molecules  are  held 
together  by  cohesion,  and  we  can  counteract  this  cohesion  by  mechan- 
ical subdivision,  reducing  the  sulphur  to  a  fine  powder ;  or  by  the 
application  of  heat  we  can  further  subdivide  the  sulphur,  melt,  and 
finally  volatize  it ;  or  we  can  throw  a  piece  of  sulphur  into  the  air, 
when  it  will  fall  back  upon  the  earth  in  consequence  of  gravitation ; 
or  we  can  dip  it  into  water,  when  it  becomes  moist  in  consequence  of 
surface-action.  Yet  in  all  these  cases  sulphur  remains  sulphur. 

It  is  entirely  different  when  sulphur  enters  into  chemical  combina- 
tion exerting  chemical  attraction,  for  instance,  when  it  burns ;  this 
means  when  it  combines  with  the  oxygen  of  the  atmospheric  air.  In 
this  case  a  new  substance,  a  disagreeably  smelling  gas,  a.  compound  of 
oxygen  and  sulphur,  is  formed. 

It  is  consequently  a  complete  change  in  the  properties  of  matter 
which  follows  the  action  of  true  chemical  attraction  ;flwe  might  define 
affinity  to  be  a  force  by  which  elements  unite  and  new  substances  are 
generated.  | 


Atoms.  Molecules,  as  stated  heretofore,  are  the  smallest  particles 
of  matter  which  can  exist.  All  matter  consists  of  molecules,  conse- 
quently the  red  oxide  of  mercury  must  also  consist  of  molecules. 

By  heating  the  oxide  of  mercury,  oxygen  and  mercury  are  obtained, 
each  of  which  also  must  consist  of  molecules.  As  the  oxide  of  mercury 


40  PRINCIPLES  OF  CHEMISTRY. 

consists  of  molecules,  and  as  these  molecules  are  neither  pure  oxygen 
nor  pure  mercury,  we  must  come  to  the  conclusion  that  a  molecule  of 
the  oxide  of  mercury  is  composed  of  a  small  particle  of  oxygen  and 
a  small  particle  of  mercury.  We  consequently  learn  that  a  molecule 
of  a  compound  substance  is  composed  of  yet  smaller  particles  of  ele- 
ments, and  these  smallest  particles  of  elements  capable  of  entering  into 
combination  are  called  atoms,  while  molecules  are  the  smallest  particles 
of  matter  which  are  capable  of  existing  in  a  free  state. 

Having  now  established  the  difference  between  atoms  and  mole- 
cules, we  may  give  a  better  definition  of  elements  and  compounds  by 
saying  that  an  elementary  substance  is  one  in  which  the  atoms  com- 
posing its  molecules  are  alike,  while  in  a  compgiuid__substance  the 
molecules  contain  atoms  of  different  kmds. 

Chemistry  is  the  science  of  affinity,  and /affinity  is  the  attraction 
acting  between  atoms  and  causing  them  to  unite  and  form  molecules/. 
As  every  chemical  change  is  due  to  the  motion  of  atoms,  chemistry 
may  also  be  defined  as  the  science  of  the  motion  of  atoms  taking  place 
in  consequence  of  chemical  ajjinity.  Also,  we  may  say  that  chemistry 
is  that  branch  of  science  which  treats  of  the  composition  of  substances, 
the  changes  in  their  composition,  and  the  laws  governing  such  changes. 

The  scheme  below  may  help  to  illustrate  the  relation  of  chemistry 
to  some  other  branches  of  physical  science : 

GENERAL  FORCE  OF  ATTRACTION, 
acting  between — 

Heavenly  bodies  Surfaces.  Molecules.  Atoms, 

or  masses. 

is  termed  : 

Gravitation.  Surface-action.  Cohesion,  Chemical  affinity. 

Adhesion. 
Capillary  attrac- 
tion, etc, 

The  phenomena  caused  by  these  respective  actions  are  considered 

by: 

Astronomy  or  Physics.  Physics. 

Mechanics.  Crystallography. 

Atomic  weight.  All  matter  possesses  weight ;  this  is  true  of  a 
mass  as  well  as  any  part  of  it,  and  must  consequently  be  true  of  the 
atoms  also  and  of  the  molecules  of  which  matter  consists.  It  is,  of 
course,  impossible  to  weigh  a  single  atom  or  a  single  molecule,  yet 


CHEMICAL  DIVISIBILITY.  41 

science  has  formed  an  opinion  in  regard  to  the  relative  weights  of 
these  minute  particles.  The  experiment  referred  to  above  may  be  so 
conducted  as  to  ascertain  the  weight  of  the  products  of  decomposition 
(viz.,  the  oxygen  and  the  mercury)  of  a  given,  previously  weighed 
quantity  of  oxide  of  mercury.  In  doing  this,  it  will  be  found  invari- 
ably that  every  13.5  parts  by  weight  of  the  oxide  of  mercury  yield 
upon  heating  12.5  parts  by  weight  of  mercury  and  1  part  of  oxygen, 
that  we  have  consequently  in  13.5  pounds  of  oxide  12.5  pounds  of 
mercury  and  1  pound  of  oxygen. 

If  we  assume  that  a  molecule  of  the  oxide  is  composed  of  one  atom 
of  mercury  and  one  atom  of  oxygen,  we  are  justified  in  saying  that  a 
mercury  atom  is  12.5  times  heavier  than  an  oxygen  atom. 

In  a  manner  similar  to  this,  the  weights  of  the  atoms  of  all  different 
elements  have  been  compared  with  each  other,  and  the  element  having 
the  lightest  atom  has  been  selected  as  the  unit  of  comparison.  The 
element  having  the  lightest  atom  is  hydrogen,  and  we  say  the  atomic  ^ 
weight  of  hydrogen  is  1,  and  compare  with  this  weight  the  weights  of 
all  other  elements.  In  doing  this,  we  find  that  the  atom  of  oxygen 
weighs  sixteen  times  as  much  as  the  atom  of  hydrogen,  and  we  con- 
sequently say  the  atomic  weight  of  oxygen  is  16. 

We  have  learned  before,  from  the  decomposition  of  the  red  oxide 
of  mercury,  that  the  mercury  atom  is  12.5  times  as  heavy  as  that  of 
oxygen.     As  the  atomic  weight  of  this  element  is  16,  the  atomic 
weight  of  mercury  must  be  12.5  times  16,  or  200. 
/     Whilst  atomic  weight  is  the  weight  of  the  atom  of  any  element  as 
/  compared  to  the  weight  of  an  atom  of  hydrogen,  molecular  weight  is 
I    the  combined  weight  of  the  atoms  forming  the  molecule.     Thus  the 
I    molecular  weight  of  oxide  of  mercury  is  200  +  16  =  216. 

Chemical  symbols.  For  reasons  to  be  better  understood  hereafter, 
chemists  designate  each  element  by  a  symbol,  and  the  first  or  first  two 
letters  of  the  Latin  name  of  the  element  have  generally  been  selected. 
Thus,  the  symbol  of  hydrogen  is  H,  of  oxygen  O,  of  mercury  Hg, 
(from  hydrargyrum),  of  sulphur  S,  etc.  These  symbols  designate, 
moreover,  not  only  the  elements,  but  one  atom  of  these  elements. 
For  instance  :  O  not  only  signifies  oxygen,  but  one  atom  or  16  parts 
by  weight  of  oxygen  ;  and  Hg,  one  atom  or  200  parts  by  weight  of 
mercury. 

Chemical  formulas.  In  a  similar  manner  as  atoms  of  elements 
are  represented  by  symbols,  the  molecules  of  a  compound  substance 


42  PRINCIPLES  OF  CHEMISTRY. 

are  designated,  and  such  a  representation  of  a  compound  substance  by 
symbols  is  called  its  formula.  Thus,  HgO  is  the  formula  of  the  red 
oxide  of  mercury,  and  it  tells  at  once  that  it  is  a  substance  composed 
of  one  atom  or  200  parts  by  weight  of  mercury,  and  one  atom  or  16 
parts  by  weight  of  oxygen. 

In  the  molecule  of  a  compound  body  there  must  be  at  least  two 
atoms,  each  one  of  a  different  element,  but  there  may  be  in  a  mole- 
cule of  a  compound  more  than  two  atoms  belonging  to  two  or  more 
elements. 

For  instance :  The  composition  of  water  is  H2O ;  this  means,  a 
molecule  of  water  contains  2  atoms  of  hydrogen  and  one  atom  of 
oxygen.  When  there  is  more  than  one  atom  of  an  element  in  a 
molecule,  the  number  of  these  atoms*  is  designated  by  placing  the 
figure  on  the  right  of  the  symbol  and  a  little  below  it,  as  in  H2O, 
whilst  2HO  or  2OH  would  designate  2  molecules  of  a  substance  con- 
taining one  atom  of  hydrogen  and  one  atom  of  oxygen. 

6.  LAWS  OF  CHEMICAL  COMBINATION. 

Law  of  the  constancy  of  composition.     This  law,  also  known 

as  the  law  of  definite  proportions,  was  the  first  ever  recognized  in 

chemical  science ;   it  was  discovered  toward  the  close  of   the  last 

century,  and  may  be  stated  thus  :  A  definite  compound  always  contains 

r  the  same  elements  in  the  same  proportion  ;  or,  in  other  words,  All  chemi- 

[   cal  compounds  are  definite  in  their  nature  and  in  their  composition. 

To  make  this  law  perfectly  understood,  the  difference  between  a 
mechanical  mixture  and  a  chemical  compound  must  be  pointed  out. 
Two  powders,  for  instance  sugar  and  starch,  may  be  mixed  together 
very  intimately  in  a  mortar,  so  that  it  seems  impossible  for  the  eye  to 
discover  more  than  one  body.  But  in  looking  at  this  powder  with 
the  aid  of  a  microscope,  the  particles  of  sugar  as  well  as  those  of 
starch  may  be  easily  distinguished.  The  mixture  thus  produced  is  a 
mechanical  mixture  of  molecule  clusters. 

QUESTIONS. — 41.  How  does  heat  act  upon  the  red  oxide  of  mercury?  42.  State 
the  difference  between  mechanical  and  chemical  divisibility.  43.  Define  the 
terms  element  and  compound.  44.  How  many  elements  and  how  many  com- 
pound substances  are  known?  45.  What  is  chemical  affinity,  and  how  does  it 
differ  from  other  forces?  46.  What  is  an  atom,  and  how  does  it  differ  from  a 
molecule?  47.  What  is  chemistry?  48.  Give  a  definition  of  atomic  weight 
and  of  molecular  weight.  49.  The  atom  of  which  element  has  been  selected 
as  the  unit  for  comparison  of  atomic  weights  ?  50.  Give  an  explanation  of 
chemical  symbols  and  formulas. 


LAWS  OF  CHEMICAL  COMBINATION.  43 

It  is  somewhat  different  when  two  substances,  for  instance  two 
metals,  are  fused  together,  or  when  two  gases  or  two  liquids  (oxygen 
and  nitrogen,  water  and  alcohol)  are  mixed  together,  or  when  finally 
a  solid  is  dissolved  in  a  liquid  (sugar  in  water).  In  these  instances 
no  separate  particles  can  be  discovered  even  by  the  microscope.  The 
mixtures  thus  produced  are  mixtures  of  molecules.  Such  mixtures 
always  exhibit  properties  intermediate  between  those  of  their  constitu- 
ents and  in  regular  gradation  according  to  the  quantity  of  each  one 
present.  The  proportions  in  which  substances  may  be  mixed  are 
variable. 

In  a  true  chemical  compound  the  proportions  of  the  constituent 
elements  admit  of  no  variation  whatever ;  it  is  not  formed  by  the  \/ 
mixing  of  molecules,  but  by  *he  combination  of  atoms  into  molecules  ; 
the  properties  of  a  compound  thus  formed  usually  differ  very  widely 
from  those  of  the  combining  elements. 

Powdered  iron  and  powdered  sulphur  may  be  mixed  together  in  many 
•different  proportions.  If  such  a  mixture  be  heated  until  the  sulphur  becomes 
liquid,  the  two  elements,  iron  and  sulphur,  combine  chemically,  but  they  do  so 
in  one  proportion  only,  56  parts  by  weight  of  iron  combining  with  32  parts  by 
weight  of  sulphur  to  form  88  parts  of  sulphide  of  iron.  If  the  two  substances 
had  been  mixed  together  in  any  other  proportion  than  the  one  mentioned,  and 
which  corresponds  to  the  atomic  weights  of  both  elements,  the  excess  of  one 
will  be  left  undisturbed  and  uncombined. 

Law  of  multiple  proportions.  If  two  elements,  A  and  B,  are 
•capable  of  uniting  in  several  proportions,  the  quantities  of  B  which 
combine  with  a  fixed  quantity  of  A  bear  a  simple  ratio  to  each  other. 
Thus  A  may  combine  with  B,  or  A  with  2  B,  or  A  with  3  B,  etc. 

This  law  was  discovered  at  the  beginning  of  the  present  century, 
when  it  was  found  that  the  ratio  of  carbon  to  hydrogen  in  olefiant 
gas,  C2H4,  is  as  6  to  1,  in  marsh  gas,  CH4,  as  6  to  2,  and  that  the 
ratio  of  carbon  to  oxygen  in  carbon  monoxide,  CO,  is  as  6  to  8,  in 
carbon  dioxide,  CO2,  as  6  to  16. 

These  and  similar  instances  led  to  the  discovery  of  the  law  of 
multiple  proportions,  and  it  was  this  law  which  led  Dalton,  in  1804, 
to  the  adoption  of  the  atomic  theory.  In  thinking  and  reasoning 
about  this  law,  he  could  find  no  other  explanation  than  that  there 
must  be  small  particles  of  definite  weight  which  combine  with  each 
other,  and  to  these  small  particles  he  gave  the  name  atoms. 

As  a  very  good  example  illustrating  the  law  of  multiple  proportions  may  be 
mentioned  the  five  compounds  formed  by  the  elements  nitrogen  and  oxygen^ 
which  compounds  have  the  composition  N2O,  N202,  N203,  N2O4,  and  N2O5, 
respectively.  In  these  compounds  we  find  16,  2X16,  3X16,  4X16,  and  5X16 
parts  by  weight  of  oxygen  in  combination  with  28  parts  by  weight  of  nitrogen. 


44 


PRINCIPLES  OF  CHEMISTRY. 


f  The  law  of  chemical  combination  by  volume,  or  the  Law  of 
I  Gay-Lussac,  may  be  stated  as  follows  :    When  two  or  more  gaseous 
I  constituents  combine  chemically  to  form  a  gaseous  compound,  the  volumes 
\of  the  individual  constituents  bear  a  simple  relation  to  the  volume  of  the 
product.     The  law  may  be  divided  into  two  laws,  thus  :  1.  Gases 
combine  by  volume  in  a  simple  ratio.     2.  The  resulting  volume  of 
the  compound,  when  in  the  form  of  a  gas,  bears  a  simple  ratio  to  the 
volumes  of  the  constituents.     For  instance  :  1  volume  of  hydrogen 
combines  with  1  volume  of  chlorine,  forming  2  volumes  of  hydro- 
chloric acid  gas  ;  2  volumes  of  hydrogen  combine  with  1  volume  of 
oxygen,  forming  2  volumes  of  water- vapor  ;  3  volumes  of  hydrogen 
combine  with  1  volume  of  nitrogen,  forming  2  volumes  of  ammonia. 
If  the  different  combining  volumes  of  the  gases  mentioned  are 
weighed,  it  will  be  found  that  there  exists  a  simple  relation  between 
these  volumes  and  the  atomic  or  molecular  weights  of  the  elements. 

For  instance  :  Equal  volumes  of  hydrogen  and  chlorine  combine, 
and  the  weights  of  these  volumes  are  as  1  : 35.4,  which  numbers 
represent  also  the  atomic  weights  of  the  two  elements.  Two  volumes 
of  hydrogen  combine  with  one  volume  of  oxygen,  and  the  weights  of 
the  volumes  are  as  1  :  8  or  2  : 16,  the  latter  being  the  atomic  weight 
of  oxygen. 


LAWS  OF  CHEMICAL  COMBINATION.  45 

The  above  diagram  shows  the  simple  relation  which  exists  between 
combining  volumes,  and  atomic  and  molecular  weights  ;  that  such  a 
relation  exists  is  not  surprising,  if  we  remember  the  law  of  Avogadro, 
which  has  been  before  stated,  and  which  says  that  all  gases  under 
equal  conditions  contain  the  same  number  of  molecules. 

The  weighing  of  equal  volumes  of  gases  consequently  is  identical 
with  the  weighing  of  equal  numbers  of  molecules.  The  molecular 
weight  of  a  substance  therefore  can  be  found  by  weighing  this  sub- 
stance in  the  gaseous  state  and  comparing  with  it  the  weight  of  an 
equal  volume  of  another  gas,  the  molecular  weight  of  which  is  known. 
The  gas  usually  adopted  for  this  comparison  is  hydrogen. 

If,  for  instance,  we  weigh  equal  volumes  of  hydrogen,  chlorine, 
oxygen,  hydrochloric  acid  gas,  and  steam,  we  find  weights  in  the 
proportion  of  2,  70.8,  32,  36.4,  and  18.  These  numbers  express 
also  the  molecular  weights  of  these  substances  ;  moreover,  they  show 
that  atomic  and  molecular  weights  of  elements  are  not  identical,  but 
that  the  latter  weight  is  twice  that  of  the  atomic  weight,  or  that  the 
v  ./molecules  of  elements  consist  of  two  atoms.1 

One  litre  of  hydrogen  at  the  freezing-point  of  water  and  under  the  ordinary 
pressure  of  15  pounds  to  the  square  inch,  weighs  0.0896  gramme.  This  weight 
of  one  litre  of  hydrogen  is  taken  as  the  unit  or  standard  of  comparison  for 
gases,  and  is  called  one  crith.  A  litre  of  oxygen  weighs  16  criths,  one  of 
chlorine  35.4  criths,  one  of  steam  9  criths,  etc. 

Theory  (Law)  of  equivalents.     Valence,  or   Quanti  valence. 
/When  one  element  replaces  another  element  in  a   compound,  the! 
I  quantities  of  the  two  elements  are  said  to  be  equivalent  to  each  other/ 
and  according  to  the  law  of  equivalents  the  replacement  of  elements 
one  by  another  takes  place  always  in  definite  proportions.     Formerly 
it  was  believed  that  the  atoms  of  all  elements  were  equivalent  one 
with  another  ;  accordingly,  atomic  weights  were  frequently  designated 
as  equivalent  weights. 

This  view,  however,  is  not  correct,  as  it  is  found  that  one  atom  of 
one  element  frequently  displaces  two  or  more  atoms  of  another 
element.  This  fact,  as  well  as  other  considerations,  has  led  to  the 
assumption  of  the  quantivalence  of  atoms.  This  property  will  be 
understood  best  by  selecting  for  consideration  a  few  compounds  of 
different  elements  with  hydrogen. 

I.  II.  III.  IV. 


HC1  H20 

HBr  H2S  H3As  H,Si 

III  H2Se  H3P 

1  A  few  exceptions  to  this  general  rule  will  be  mentioned  in  the  proper  places. 


46  PRINCIPLES  OF  CHEMISTRY. 

We  see  here  that  Cl,  Br,  and  I  combine  with  H  in  the  proportion 
of  atom  for  atom  ;  O,  S,  Se  combine  with  H  in  the  proportion  of  2 
atoms  of  hydrogen  for  1  atom  of  the  other  element ;  N,  As,  P  com- 
bine with  3 ;  C  and  Si  with  4  atoms  of  hydrogen. 

Moreover,  it  has  been  found  that  the  compounds  mentioned  in 
column  I.  are  the  only  ones  which  can  be  formed  by  the  union  of 
the  elements  Cl,  Br,  and  I  with  H.  They  invariably  combine  in  this 
proportion  only.  Other  elements  show  a  similar  behavior.  For 
instance,  the  metal  sodium  combines  with  chlorine  or  bromine  in  one 
proportion  only,  forming  the  compound  NaCl  or  NaBr. 

Looking  at  columns  II.,  III.,  and  IV.,  we  see  that  the  elements 
mentioned  there  combine  with  2,  3,  and  4  atoms  of  hydrogen, 
respectively.  It  is  evident,  therefore,  that  there  must  be  some  pecu- 
liarity in  the  power  of  attraction  of  different  elements  toward  other 
elements,  and  to  this  property  of  the  atoms  of  elements  of  hoi rh' 110- 
in  combination  one,  two,  three,  four,  or  more  atoms  of  other  ele- 
ments the  name  atomicity,  quantivalence,  or  simply  valence,  has  been 
given. 

According  to  this  theory  of  the  valence  of  atoms,  we  distinguish 
univalent,  bivalent,  trivalent,  quadrivalent,  quinquivalent,  sexivalent, 
arid  septivalent  elements.  €^11  pflpmpnts  which  combine_with  hydro- 
gpnrn^fVip  proportion  of  one  atom  to  one  atomare  univalent,  as,  for 
instance,  Cl,  Br,  I,  F,  and  all  elements  which  combine  with  these  in 
but  one  proportion,  that  is,  atom  with  atom,  bear  the  same  valence, 
or  are  also  univalent,  as,  for  instance,  Na,  K,  Ag,  etc. 

Those  elements  which  combine  with  hydrogen  or  other  univalent 
elements  in  the  proportion  of  one  atom  to  two  atoms  are  bivalent, 
such  as  O,  S,  Se. 

Trivalent  and  quadrivalent  elements  are  those  the  atoms  of  which 
combine  with  3  or  4  atoms  of  hydrogen,  respectively.  Figuratively 
speaking,  we  may  say  that  the  atoms  of  univalent  elements  have  but 
one,  those  of  bivalent  elements  two,  of  trivalent  elements  three,  of 
quadrivalent  elements  four  bonds  or  points  of  attraction,  by  means  of 
which  they  may  attach  themselves  to  other  atoms. 

C    Elementary  atoms  are  often  named  according  to  their  valence  !| 
nonads,  diads,  triads,  tetrads,  pentads,  hexads,  and  heptads.  / 

To  indicate  the  valence  of  the  elements  frequently  dots  or  numbers 
are  placed  above  the  chemical  symbols,  thus  IT,  Ou,  Nli!,  Cmi  or  Civ. 
The  bonds  are  often  graphically  represented  by  lines,  thus : 


H-     -0-, 


— N— ,    _C 


LAWS  OF  CHEMICAL  COMBINATION.  47 

It  is  needless  to  say  that  such  representations  are  merely  symbolical, 
and  express  the  view  that  atoms  have  a  definite  power  to  combine 
with  others. 

*When  atoms  combine  with  one  another  the  bonds  are  said  to  be 
satisfied,  and  it  is  graphically  expressed  thus : 

H  H 

H— Cl,    H— O— H    or    O/    ,    H— N— H    or    N— H 

X-H 

Whilst  the  valence  of  some  elements  is  invariably  the  same  under 
all  circumstances,  other  elements  show  a  different  valence  (this  means 
a  different  combining  power  for  other  atoms)  under  different  condi- 
tions.    For  instance :  Phosphorus  combines  both  with  3  and  5  atomsV 
of  chlorine,  forming  the  compounds  PC13  and  PC15.     As  chlorine  is/ 
a  univalent  element,  we  have  to  assume  that  phosphorus  has  in  one 
case  3,  in  another  case  5  points  of  attraction.    Many  similar  instances 
are  known,  and  will  be  spoken  of  later. 

The  only  explanation  which  we  can  furnish  in  regard  to  the  variability  of 
the  valence  of  atoms  is  the  assumption  that  sometimes  one  or  more  of  the 
bonds  of  an  atom  unite  with  other  bonds  of  the  same  atom.  If,  for  instance, 
in  the  quinquivalent  phosphorus  atom  two  bonds  unite  with  one  another  a 
trivalent  atom  will  remain. 

It  is  noticed  invariably  that  the  valence  of  atoms  increases  or  diminishes  by 
two,  which  could  not  be  otherwise,  if  the  explanation  given  be  correct.  Thus 
chlorine,  the  valence  of  which  generally  is  I.,  may  also  have  a  valence  equal 
to  III.,  V.,  or  VII.,  while  sulphur  shows  a  valence  either  of  II.,  IV.,  or  VI. 
Atoms  whose  valence  is  even,  as  in  case  of  sulphur,  are  called  artiads ;  those 
whose  valence  is  expressed  in  uneven  numbers,  as  chlorine  and  phosphorus, 
are  called  perissads. 

While  it  is  now  being  assumed  that  most  of  the  elements  possess  more  than 
one  valence,  in  consequence  of  the  assumed  power  of  bonds  in  the  same  atom 
to  saturate  one  another,  in  this  book  will  be  mentioned  chiefly  that  valence 
which  the  element  seems  to  possess  predominantly. 

The  doctrine  of  the  valence  of  atoms  has  modified  our  views  of  the 
equivalence  of  atoms v  We  now  say  that  all  atoms  of  a  like  valence \ 
are  equivalent  to  each  other.v'  The  atoms  of  each  univalent  element  / 
are  equivalent  to  each  other,  and  so  of  the  atoms  of  any  other  valence, 
but  two  atoms  of  a  univalent  element  are  equivalent  to  one  atom  of 
a  bivalent  element,  or  two  atoms  of  a  bivalent  element  to  one  atom 
of  a  quadrivalent  element,  etc. 

After  having  explained  this  valence  of  atoms,  it  now  may  be  better 
understood  why  the  atoms  in  an  element  do  not  exist  in  a  free  or 


48  PRINCIPLES  OF  CHEMISTRY. 

tincombined  state,  but  combine  with  each  other  to  form  molecules. 
Atoms  having  the  tendency  of  combining  with,  or  attaching  them- 
selves to  other  atoms,  are  bound  to  exert  that  attraction,  and  if  they 
are  not  combined  with  atoms  of  other  elements,  they  combine  with 
each  other.  For  instance:  Oxygen  gas  is  not  a  mass  of  oxygen 
atoms,  but  of  oxygen  molecules,  each  molecule  being  formed  by  the 
union  of  two  atoms. 


7.  DETEEMINATION  OF  ATOMIC  AND  MOLECULAR  WEIGHTS.1 

Determination  of  atomic  weights  by  chemical  decomposition. 
The  great  difficulties  originally  encountered  in  the  determination  of 
atomic  weights  cannot  well  be  described  here.  Consideration  will  be 
given  alone  to  the  three  principal  methods  at  present  in  use.  These 
methods  depend  either  on  chemical  action  or  on  physical  properties. 

One  of  the  chemical  methods  used  for  the  determination  of  atomic 
weights  has  been  stated  before  in  describing  the  decomposition  of  the 
red  oxide  of  mercury  by  heat.  The  principle  of  this  method  is  the 
determination  of  the  proportions  by  weight  in  which  the  element,  the 
atomic  weight  of  which  is  unknown,  combines  with  an  element  the 
atomic  weight  of  which  is  known.  For  instance:  If  in  decomposing 
a  substance  we  find  it  to  contain  in  72  parts  by  weight,  16  parts  by 
weight  of  oxygen  and  56  parts  by  weight  of  another  element,  we 
have  a  right  to  assume  the  atomic  weight  of  this  second  element  to  be 
56,  provided,  however,  that  the  compound  is  actually  formed  by  the 
union  of  one  atom  of  oxygen  and  one  atom  of  the  other  element. 
These  56  parts  by  weight  might,  however,  represent  2  or  3  or  more 

QUESTIONS.— 51.  State  the  law  of  the  constancy  of  composition.  52.  What 
is  the  difference  between  a  mixture  and  a  chemical  compound  ?  53.  Mention 
some  instances  of  the  production  of  molecular  mixtures.  54.  State  the  law  of 
multiple  proportions.  55.  What  considerations  led  Dalton  to  the  adoption  of 
the  atomic  theory?  56.  What  regularity  regarding  volume  is  noticed  when 
gases  combine  chemically?  57.  To  what  was  the  term  equivalent  quantities 
applied  formerly,  and  what  is  to  be  understood  by  it  to-day?  58.  Explain  the 
term  quantivalence  or  atomicity.  59.  Mention  some  univalent,  bivalent,  tri- 
valent,  and  quadrivalent  elements.  60.  Suppose  a  certain  volume  of  hydrogen 
to  weigh  20  grains,  how  much  will  an  equal  volume  of  oxygen  and  how  much 
will  an  equal  volume  of  hydrochloric  acid  gas  weigh,  provided  pressure  and 
temperature  be  the  same  ? 

i  The  consideration  of  Chapter  7  should  be  postponed  until  the  student  has  become  familiar 
with  chemical  phenomena  generally. 


DETERMINATION  OF  ATOMIC  WEIGHTS.  49 

atoms.     If  56  represented  2  atoms,  the  atomic  weight  would  be  but 
28;  if  4  atoms,  14. 

As  this  mode  of  determination  gives  no  clue  to  the  number  of 
atoms  present  in  the  molecule,  the  results  obtained  are  liable  to  be 
incorrect.  In  fact,  the  atomic  weights  of  a  number  of  elements  had 
originally  been  determined  incorrectly  by  using  the  above  or  similar 
methods,  and  many  of  these  old  atomic  weights  had  to  be  changed 
(generally  doubled)  in  order  to  obtain  the  correct  numbers. 

Thus,  in  examining  water,  it  was  found  that  it  contained  8  parts 
by  weight  of  oxygen  to  1  part  of  hydrogen,  and  the  conclusion  was 
drawn  that  the  atomic  weight  of  oxygen  was  8,  and  that  the  molecule 
of  water  was  formed  by  the  union  of  one  atom  of  hydrogen  and  one 
atom  of  oxygen.  It  will  be  demonstrated  below  why  we  assume  to- 
day that  the  atomic  weight  of  oxygen  is  16,  and  that  the  molecule  of 
water  is  composed  of  2  atoms  of  hydrogen  and  1  of  oxygen. 

Another  chemical  method  of  determining  atomic  weights  is  the 
replacement  of  hydrogen  atoms  in  a  known  substance  by  the  element 
the  atomic  weight  of  which  is  to  be  determined.  For  instance :  Hy- 
drochloric acid  is  composed  of  one  atom  of  chlorine  weighing  35.4, 
and  one  atom  of  hydrogen  weighing  1,  the  molecular  weight  of  hy- 
drochloric acid  being  36.4.  If  in  this  acid  the  hydrogen  be  replaced 
by  some  other  element,  for  instance  by  sodium,  we  are  enabled  to 
determine  the  atomic  \veight  of  sodium  by  weighing  its  quantity  and 
that  of  the  liberated  hydrogen.  Suppose  that  by  the  action  of  36.4 
grammes  of  hydrochloric  acid  on  sodium,  1  gramme  of  hydrogen 
was  replaced  by  23  grammes  of  sodium.  In  that  case  we  would  say 
that  the  atomic  weight  of  sodium  is  equal  to  23. 

The  difficulty  which  was  alluded  to  above  exists  also  in  this  mode 
of  determination  of  atomic  weights,  viz.,  not  knowing  whether  it 
was  actually  one  atom  of  sodium  that  replaced  the  one  part  of  hy- 
drogen, a  doubt  is  left  as  to  whether  or  not  the  determination  is  correct. 

Determination  of  atomic  weights  by  means  of  specific  weights 
of  gases  or  vapors.  It  has  been  stated  before  that  equal  volumes  of 
gases  contain,  under  like  conditions,  the  same  number  of  molecules 
(no  matter  how  few  or  many  the  atoms  within  the  molecules  may  be), 
and  that  the  molecules  of  elements  contain  (in  most  cases)  two  atoms. 
These  facts  give  in  themselves  the  necessary  data  for  the  determina- 
tion of  atomic  weights. 

For  instance :  If  a  certain  volume  of  hydrogen  is  found  to  weigh 
2  grammes,  and  an  equal  volume  of  some  other  gaseous  element  is 

4 


50  PRINCIPLES  OF  CHEMISTRY. 

found  to  weigh  71  grammes,  then  the  atomic  weight  of  the  latter 
element  must  be  35.5,  because  2  and  71  represent  the  relative  weights 
of  the  molecules  of  the  two  elements.  Each  molecule  being  com- 
posed of  2  atoms,  these  molecular  weights  have  to  be  divided  by  2  in 
order  to  find  the  atomic  weights,  which  are,  consequently,  1  and  35.5 
respectively. 

In  comparing  by  this  method  oxygen  with  hydrogen,  it  is  found 
that  equal  volumes  of  these  gases  weigh  32  and  2  respectively,  that 
the  atomic  weight  of  oxygen  is  consequently  16,  and  not  8,  as  deter- 
mined by  chemical  methods. 

This  mode  of  determining  atomic  weights  may  be  applied  to  all 
elements  which  are  gases  or  which  may  without  decomposition  be 
converted  into  gas.  There  are,  however,  elements  which  cannot  be 
volatilized,  and  in  this  case  it  becomes  necessary  to  determine  the 
specific  gravity  of  some  gaseous  compound  of  the  element.  The 
element  carbon  itself  has  never  been  volatilized,  but  we  know  many 
of  its  volatile  compounds,  and  these  may  be  used  in  the  determina- 
tion of  its  atomic  weight. 

Determination  of  atomic  weights  by  specific  heat.  Specific 
heat  has  been  stated  to  be  the  quantity  of  heat  required  to  raise  the 
temperature  of  a  given  weight  of  any  substance  a  given  number  of 
degrees,  as  compared  with  the  quantity  of  heat  required  to  raise  the 
temperature  of  the  same  weight  of  water  the  same  number  of  degrees. 

In  comparing  atomic  weights  with  the  numbers  expressing  the  spe- 
cific heats,  it  is  found  that  the  higher  the  atomic  weight  the  lower  the 
specific  heat,  and  the  lower  the  atomic  weight  the  higher  the  specific 
heat.  This  simple  relation  may  be  thus  expressed  :  Atomic  weighl 
are  inversely  proportional  to  the  specific  heats;  or  the  product  of  the! 
atomic  weight  multiplied  by  the  specific  heat  is  a  constant  quantity^ 
for  the  elements  examined. 

Elements.          Specific  heats.                Atomic  weights.  Product  of  specific  heat 

( Water  =  1.)  X  atomic  weight. 

Lithium,             09408  7  6.59 

Sodium,               0.2934  23  6.75 

Sulphur,              02026  32  648 

Zinc,                    00956  65  6.22 

Bromine  (solid),  0.0843  80  6  75 

Silver,                  0.0570  108  6.16 

Bismuth,             0.0308  209  644 

An  examination  of  this  table  will  show  this  relation  between 
atomic  weight  and  specific  heat,  and  also  that  the  product  of  atomic 
weight  multiplied  by  specific  heat  is  equal  to  about  6.5.  The  varia- 


DETERMINATION  OF  ATOMIC  WEIGHTS.  5| 

tions  noticed  in  this  constant  quantity  of  about  6.5  may  be  due  to 
errors  made  in  the  determinations  of  the  specific  heats,  and  subse- 
quent determinations  may  cause  a  more  absolute  agreement. 

However,  the  agreement  is  sufficiently  close  to  justify  the  deduction 
of  a  law  which  says  :  T/ie  atoms  of  all  elements  have  exactly  the  same 
capacity  for  heat.  This  law  was  first  recognized  by  Dulong  and  Petit 
in  1819,  and  is  simply  a  generalization  of  the  facts  stated. 

To  show  more  clearly  what  is  meant  by  saying  that  all  atoms  have 
the  same  capacity  for  heat,  we  will  select  three  elements  to  illustrate 
this  law. 

If  we  take  of  lithium  7  grammes,  of  sulphur  32  grammes,  of  silver 
108  grammes,  we  have  of  course  in  these  quantities  equal  numbers  of 
atoms,  because  7,  32,  and  108  ^represent  the  atomic  weights  of  these 
elements.  If  we  expose  these  stated  quantities  of  the  three  elements  to 
the  same  action  of  heat,  we  shall  find  that  the  temperature  increases 
equally  for  all  three  substances — that  is  to  say,  the  same  heat  will  be 
required  to  raise  7  grammes  of  lithium  1°,  which  is  necessary  to  raise 
either  32  grammes  of  sulphur  or  108  grammes  of  silver  1°. 

(The  quantity  of  heat  necessary  to  raise  the  atom  of  any  element  aj 
certain  number  of  degrees  is,  consequently,  the  same.  As  heat  is  the/ 
consequence  of  motion,  the  result  of  the  facts  stated  may  also  be  ex- 
pressed by  saying :  It  requires  the  same  energy  to  cause  different 
atoms  to  vibrate  with  such  a  velocity  as  to  acquire  the  same  tempera- 
ture, no  matter  whether  these  atoms  be  light  or  heavy. 

It  is  evident  that  these  facts  give  us  another  means  of  determining 
atomic  weights,  by  simply  dividing  6.5  by  the  specific  heat  of  the  ele- 
ment. The  specific  heat  of  sulphur,  for  instance,  has  been  found  to  be 
0.2026.  6.5  divided  by  this  number  is  31.6,  or  nearly  32.  Originally 
the  atomic  weight  of  sulphur  had  been  determined  by  chemical  methods 
to  be  16,  but  its  specific  heat,  as  well  as  other  properties,  has  shown 
this  number  to  be  but  one-half  of  the  weight,  32,  now  adopted. 
f  It  may  be  mentioned  that  elements  possess  essentially  the  samg 
\specific  heat  whether  they  exist  in  a  free  state  or  are  in  combination ; 
this  fact  will,  in  many  cases,  be  of  use  in  the  determination  of  atomic 
weights. 

Determination  of  molecular  weights.  From  the  statements 
made  regarding  the  determination  of  atomic  weights,  it  is  evident 
that  we  may  use  a  number  of  methods  for  determining  molecular 
weights,  these  methods  being  to  some  extent  analogous  to  the  former. 

Thus  we  have  methods  which  are  based  entirely  on  chemical  analysis 


52  PRINCIPLES  OF  CHEMISTRY. 

or  on  chemical  changes  generally.  If,  for  instance,  the  analysis  of  a 
substance  shows  of  calcium  40  per  cent.,  of  carbon  12  per  cent.,  and 
of  oxygen  48  per  cent.,  we  have  a  right  to  assume  that  the  molecule  is 
made  up  of  1  atom  of  calcium,  1  atom  of  carbon,  and  3  atoms  of 
oxygen,  as  the  atomic  weights  of  these  elements  are  40,  12,  and  16 
respectively.  The  molecular  weight  in  this  case  is  100,  and  the  com- 
position is  expressed  by  the  formula  CaCO3,  but  the  molecular  weight 
might  be  200  and  the  correct  formula  Ca2C2O6.  There  are  actually 
substances  which  contain  such  multiples  of  atoms,  as,  for  instance,  the 
compounds  C2H2  and  C6H6,  and  as  their  percentage  composition  is 
identical,  analytical  methods  are  insufficient  to  indicate  the  number 
of  atoms  contained  in  these  molecules. 

The  second  method,  based  on  Avoggdro's  law,  is  applicable  to  all 
substances  which  are  or  can  be  converted  into  gases  or  vapors  without 
decomposition.  Weighing  equal  volumes  of  hydrogen  and  of  some 
other  substance  in  the  gaseous  state  gives  at  once  the  data  for  calcu- 
lating the  molecular  weight.  (See  page  44.) 

A  third  method,  that  of  Raoult,  is  based  upon  the  fact  that  the 
freezing-point  of  a  liquid  is  lowered  to  the  same  extent  by  dissolving 
in  it  compounds  in  quantities  proportional  to  their  molecular  weights. 
For  example  :  Water  begins  to  solidify  at  32°  F.  (0°  C.),  but  by  dis- 
solving in  it  say  4  per  cent,  of  its  weight  of  a  salt  (the  molecular  weight 
of  which  is  known)  the  freezing-point  is  lowered,  say  1°  C.  If,  then, 
another  salt  (the  molecular  weight  of  which  is  not  known)  be  dissolved 
in  water,  and  it  be  found  that  to  reduce  the  freezing-point  1°  C.  there 
must  be  dissolved  a  quantity  equal  to  7  per  cent,  of  the  weight  of  the 
water  used — then  are  the  molecular  weights  of  the  two  salts  to  each 
other  as  is  4  to  7. 

In  regard  to  this  method  of  Raoult  it  should  be  stated  that  it  is 
applicable  only  to  such  substances  as  do  not  act  chemically  upon  the 

QUESTIONS.— 61.  What  are  the  three  principal  methods  used  for  the  deter- 
mination of  atomic  weights  ?  62.  Why  are  chemical  means  not  always  sufficient 
to  determine  atomic  weights  ?  63.  How  can  the  specific  gravity  of  elements  in 
the  gaseous  state  be  used  for  the  determination  of  atomic  weight  ?  64.  Describe 
a  method  of  the  determination  of  atomic  weight  by  chemical  means.  65.  State 
one  of  the  reasons  why  the  atomic  weight  of  oxygen  has  been  changed  from  8 
to  16.  66.  What  relation  exists  between  atomic  weight  and  specific  heat? 
67.  State  the  law  of  Dulong  and  Petit.  68.  Suppose  the  specific  heat  of  an 
element  to  be  0.1138,  what  will  its  atomic  weight  be  ?  69.  Suppose  the  specific 
gravity  of  an  elementary  gas  to  be  14,  what  will  its  atomic  weight  be  ?  70.  Sup- 
pose 216  grammes  of  an  element  replace  2  grammes  of  hydrogen  in  73  grammes 
of  HC1,  what  will  the  atomic  weight  of  the  element  be  ? 


DECOMPOSITION  OF  COMPOUNDS.  53 

solvent  used,  and  that  the  ratio  of  the  lowering  of  the  freezing-point 
is  not  the  same  for  all  substances,  but  only  for  members  of  the  same 
class  of  substances. 


8.  DECOMPOSITION  OF  COMPOUNDS.    GROUPS  OF  COMPOUNDS. 

Action  of  heat  upon  compounds.  All  phenomena  taking  place 
in  nature  are,  without  exception,  due  to  motion.  Chemistry  considers 
the  motion  of  atoms,  without  which  no  chemical  change  takes  place. 
The  causes  for  chemical  changes  are  either  physical  actions  (heat, 
light,  electricity),  or  the  decomposing  influence  of  one  substance  upon 
another  caused  by  the  atoms  rearranging  themselves  into  new  bodies, 
so  as  to  better  satisfy  their  affinities. 

The  decomposing  action  of  heat  upon  compounds  has  been  men- 
tioned before  in  connection  with  the  decomposition  of  red  oxide  of 
mercury  into  mercury  and  oxygen.  Similarly  to  this  process,  many 
other  compound  substances  are  decomposed  by  heat  either  into  ele- 
ments, or,  more  frequently,  into  simpler  forms  of  combination.  This 
means  that  the  molecule  of  a  .substance  containing,  for  instance,  10 
atoms,  is  split  up  into  2,  3,  or  more  molecules,  each  one  containing  a 
portion  of  the  10  atoms. 

For  instance :  A  piece  of  marble,  which  is  calcium  carbonate,  or 
CaCO3,  is  decomposed  by  heat  into  calcium,  oxide,  CaO,  and  carbon 
dioxide,  CO2. 

That  heat  has  such  decomposing  influence  upon  compounds  is  readily 
accounted  for,  if  we  bear  in  mind  that  increase  in  heat  means  increased  molec- 
ular vibration,  which  most  likely  weakens  the  stability  of  the  molecule,  and 
diminishes  the  attractions  of  its  component  atoms.  On  the  other  hand,  heat 
will  in  many  cases  facilitate  chemical  combination  between  two  substances, 
because  the  increased  molecular  vibration  brings  the  molecules  closer  within 
the  sphere  of  each  other's  attraction,  thereby  facilitating  chemical  union.  For 
instance :  Mercury  and  oxygen  do  not  act  upon  each  other  at  ordinary  tem- 
perature, but  when  heated  to  a  temperature  somewhat  below  the  boiling-point 
of  mercury,  they  combine  slowly,  forming  oxide  of  mercury.  This  compound, 
however,  as  shown  before,  readily  decomposes  into  mercury  and  oxygen  when 
heated  to  a  low  red  heat. 

The  quantity  of  heat  required  for  decomposition  differs  widely 
according  to  the  nature  of  the  substance.  Some  substances  can  be 
produced  only  at  a  temperature  below  the  freezing-point  of  water,  a 
higher  temperature  causing  their  decomposition ;  other  substances  may 
be  decomposed  at  temperatures  between  the  freezing-  and  boiling- 


54  PRINCIPLES  OF  CHEMISTRY. 

points ;  others  again,  and  to  these  belong  the  majority  of  inorganic 
compounds,  may  be  raised  to  red  or  white  heat  before  decomposition 
sets  in  ;  and  still  another  number  of  compounds  have  never  yet  been 
decomposed  by  heat.  /  Theoretically ,  however,  we  assume  that  all 
compounds  may  be  decomposed,  by  heat,  should  it  be  possible  to  raise 
it  to  a  sufficiently  high  degree.  ] 

Decomposition  by  electricity.  Similarly  to  heat,  also  electricity 
decomposes  many  substances,  provided  they  are  in  a  liquid  or  gaseous 
state.  These  decompositions  are  usually  accomplished  by  allowing  an 
electric  current  to  pass  through  the  liquid,  or  electric  sparks  to  pass 
through  the  gas.  Thus  hydrochloric  acid,  HC1,  may  be  decomposed 
into  hydrogen  and  chlorine;  water,  H^O,  into  hydrogen  and  oxygen. 

The  act  of  decomposing  a  compound  by  electricity  is  known  as  electrolysis, 
and  the  substance  thus  decomposed  is  termed  electrolyte.  During  the  decom- 
position of  substances  by  electrolysis  one  of  the  products  of  decomposition 
appears  at  the  negative,  the  other  at  the  positive  pole  of  the  battery.  Trnn, 
when  water  is  decomposed,  the  hydrogen  is  evolved  from  the  negative,  the 
oxygen  from  the  positive  pole.  Or,  when  salts  are  decomposed,  the  metal  is 
deposited  at  the  negative  pole,  and  the  acid,  or  its  decomposition  products  at 
the  positive  pole. 

It  was  formerly  believed  that  those  elements  which  in  electrolysis  appear  at 
the  negative  pole  were  charged  with  positive  electricity,  and  were  called  electro- 
positive elements,  while  those  appearing  at  the  positive  pole  were  charged  with 
negative  electricity  and  called  electro-negative  elements.  According  to  this  view 
the  non-metals  are  electro-negative,  while  the  metals  are  electro-positive. 

There  is  a  certain  relation  between  electrical  and  chemical  action,  as 
the  quantity  of  electricity  which,  for  instance,  sets  free  35.4  grammes 
of  chlorine,  will  also  set  free  80  grammes  of  bromine  or  127  grammes 
of  iodine.  The  figures  35.4,  80,  and  127  represent  the  atomic  weights 
of  these  elements. 

Decomposition  by  light.  Another  cause  of  decomposition  is,  in 
many  cases,  the  action  of  light.  The  art  of  photography  is  based 
upon  this  kind  of  decomposition.  Many  substances,  easily  affected 
by  light,  have  to  be  kept  in  the  dark  to  prevent  them  from  being 
decomposed. 

The  phenomena  of  heat,  light,  and  electricity  resemble  each  other  in  so  far 
as  they  are  phenomena  of  motion.  Heat  is  the  consequence  of  the  motion  of 
material  particles  (molecules);  light  is  the  consequence  of  the  vibratory  motion 
of  the  hypothetical  medium  ether ;  probably  the  same  is  true  of  electricity. 

These  motions,  in  being  transferred  to  atoms,  have,  as  shown  above,  frequently 
the  tendency  of  splitting  up  the  molecules  of  compound  substances. 


DECOMPOSITION  OF  COMPOUNDS.  55 

Mutual  action  of  substances  upon  each  other.  As  a  general 
rule,  it  may  be  said  that  no  chemical  action  takes  place  between  two 
substances  both  of  which  are  in  the  solidj3ta£e,  because  the  molecules 
do  not  come  in  sufficiently  close  proximity  to  exchange  their  atoms. 
The  free  motion  of  the  molecules  in  liquid  or  gaseous  substances 
facilitates  such  a  proximity,  and  consequently  chemical  action.  It  is 
often  sufficient  to  have  but  one  of  the  acting  substances  in  the  gaseous 
or  liquid  state,  while  the  second  one  is  a  solid.  By  converting  two 
solids  into  extremely  fine  powder  and  mixing  them  together  thor- 
oughly, chemical  combination  may  follow,  provided  the  affinity 
between  them  be  sufficiently  strong. 

The  action  of  substances  upon  each  other  may  be  represented  by 
the  following  equations,  in  which  the  letters  stand  for  elements  or 
groups  of  elements  : 

1.  A    +  B    =AB  =  direct  combination. 

2.  AB  -f  C    =  AC  -f  B     =  direct  decomposition. 

3.  AB  +  CD  =  AC  +  BD  =  double  decomposition. 

As  instances  illustrating  the  above,  may  be  mentioned  the  fol- 
lowing chemical  reactions  : 

1.  H       '+       Cl       =       HC1. 

Hydrogen.          Chlorine.       Hydrochloric  acid. 

The  formula  here  given  for  the  formation  of  hydrochloric  acid  is 
not  entirely  correct,  because  the  action  between  hydrogen  and  chlo- 
rine does  not  take  place  between  free  atoms,  but  between  the  mole- 
cules of  the  two  elements,  each  molecule  containing  two  atoms.  The 
more  correct  way  of  writing  the  formula  would  therefore  be  : 

HH       +       C1C1    =    2HC1. 
Or 

2H         +        2C1      =    2HC1. 

2.  Hydrochloric   acid   and    sodium   form   sodium    chloride    and 

hydrogen  : 

HC1     +     Na    =    NaCl     +     H. 

The  formula  more  correctly  written  would  be  : 
2HC1     -f-    2Na    =    2NaCl    +    2H. 

3.  HC1    +     AgNO3    =    AgCl    +    HNO3. 

Hydrochloric         Silver  Silver  Nitric  acid, 

acid.  Nitrate.  Chloride. 

This  form  of  decomposition,  known  as  double  decomposition  or 
metathesis,  is  one  of  the  common  kinds  of  chemical  changes  met  with, 
in  chemical  operations. 


56  PRINCIPLES  OF  CHEMISTRY. 

All  the  decompositions  mentioned  above  are  caused  by  the  affinity 
which  the  atoms  of  one  substance  have  for  atoms  of  another  substance. 
For  instance  :  The  decomposition  of  hydrochloric  acid  by  sodium 
may  be  explained  by  saying  that  sodium  has  a  greater  affinity  for 
chlorine  than  for  hydrogen,  as  the  latter  is  expelled  by  the  sodium. 

No  general  rule  can,  however,  be  given  for  the  intensity  of  affinity 
with  which  the  atoms  of  different  elements  attract  each  other,  because 
this  attraction  differs  under  different  conditions.  For  instance: 
Water  passed  in  the  form  of  steam  over  red-hot  iron  is  decomposed, 
iron  oxide  and  free  hydrogen  being  formed  : 

Fe    +    H2O    =    FeO     +     2H. 

This  decomposition  would  indicate  that  the  attraction  between  iron 
and  oxygen  is  greater  than  between  hydrogen  and  oxygen.  But  in 
passing  free  hydrogen  over  heated  iron  oxide  the  reverse  action 
takes  place,  water  and  free  iron  being  formed  : 

FeO     +     2H    =    Fe     +    H2O. 

This  reaction  would  indicate  that  the  affinity  between  oxygen  and 
hydrogen  is  greater  than  between  oxygen  and  iron. 

As  a  general  rule  it  may  be  stated  that  the  quantity  of  a  product 
formed  by  chemical  action  of  two  substances  upon  one  another  is 
influenced  by  the  relative  proportions  of  the  reacting  substances.  In 
the  above  instance  iron  decomposes  water  when  the  iron  is  in  large 
excess,  while  a  liberal  supply  of  hydrogen  causes  the  reverse  action. 
As  a  second  instance  may  be  mentioned  the  decomposition  of  sodiuin 
nitrate  by  sulphuric  acid,  with  the  formation  of  sodium  acid  sulphate 
and  free  nitric  acid.  On  the  other  hand,  sodium  acid  sulphate  is 
decomposed  by  a  large  excess  of  nitric  acid  into  sodium  nitrate  and 
free  sulphuric  acid. 

A  consideration  of  this  mass-action,  as  it  is  now  termed,  has  led  to 
the  establishment  of  the  law,  that*  Chemical  action  is  proportional  to 
the  active  mass  of  each  substance  taking  part  in  the  change,  j 

While  the  power  of  affinity  possessed  by  atoms  or  compounds  does 
not  furnish  us  with  data  sufficient  to  predict  all  chemical  changes,  we 

y  lay  down  a  general  rule  which  governs  the  decomposition  of 

rtain  compounds  and  which  may  be  stated  thus  /  When  two  (or 
more)  substances  are  brought  together  in  solution,  which  substances  by 
any  rearrangement  of  the  atoms  may  form  a  product  insoluble  in  the 
quid  present,  this  product  will  form  and  separate  as  a  precipitate. 

As  instances  of  this  kind  of  decomposition  may  be  mentioned  the 
formation  of  all  the  hundreds  of  insoluble  metallic  salts,  which  are 


DECOMPOSITION  OF  COMPOUNDS.  57 

produced  by  the  action  of  one  salt  solution  upon  another  salt  solution, 
the  first  solution  containing  a  metal  which  with  the  acid  of  the  second 
solution  may  form  an  insoluble  compound,  which  is  then  invariably 
produced  as  a  precipitate.  For  instance  :  Calcium  carbonate,  CaCO3, 
is  insoluble ;  if  we  bring  together  two  solutions  containing  a  soluble 
calcium  salt  and  a  soluble  carbonate,  such  as  calcium  chloride,  CaCl2r 
and  sodium  carbonate,  Na2CO3,  calcium  carbonate  is  precipitated. 

A  second  general  rule  may  be  stated  thus :  When  two  substances 
capable  of  forming  a  volatile  product  are  brought  together,  the  reaction 
generally  takes  place.  As  instances  may  be  mentioned  the  liberation 
of  carbon  dioxide  from  any  carbonate  by  the  action  of  an  acid,  and 
the  liberation  of  ammonia  gas  from  ammonium  compounds  by 
calcium  hydroxide. 

The  nascent  state.  This  expression  is  used  of  elements  at  the 
moment  when  their  atoms  leave  molecules  and  have  not  yet  had  time 
to  reenter  into  combination.  When  in  this  state  the  atoms  have  a 
much  greater  energy  to  combine  than  after  having  entered  into  a 
combination  with  other  atoms  of  either  the  same  kind  (to  form 
elementary  molecules)  or  of  another  kind  (to  form  compound  mole- 
cules). White  arsenic,  As2O3,  is  a  compound  of  the  metal  arsenic 
with  oxygen  ;  if  through  a  solution  of  this  compound  hydrogen  gas 
be  allowed  to  pass,  no  chemical  change  takes  place.  If,  however, 
hydrogen  be  generated  or  set  free  in  a  solution  of  white  arsenic,  then 
the  hydrogen  atoms,  while  in  the  nascent  state,  have  sufficient  energy 
to  combine  with  both  the  elements  arsenic  and  oxygen,  forming 
arsenetted  hydrogen  or  arsin,  AsH3,  and  water,  H2O. 

Chemical  reaction  in  its  broader  sense  refers  to  any  chemical 
change,  but  is  used  more  especially  when  the  intention  is  to  stiTdy 
the  nature  of  the  substances  decomposed  or  formed.  The  expression 
reaqentjs  applied  to  those  substances  used  for  bringing  about  such 


Analysis  and  synthesis.  These  terms  refer  to  two  methods  of 
research  in  chemistry,  accomplished  by  two  kinds  of  reaction,  analyti- 
and  synthetical. 

Analysis  is  that  mode  of  research  by  which  compound  substances 
are  broken  up  into  their  elements  or  into  simpler  forms  of  combina- 
tion, and  analytical  reactions  are  all  chemical  processes  by  which  the 
nature  of  an  element,  or  of  a  group  of  elements,  may  be  recognized. 


,58  PRINCIPLES  OF  CHEMISTRY. 

A 

/     Synthesis  is  that  method  of  research  by  which  bodies  are  made  to 

vunite  to  produce  substances  more  complex. 

Analytical  and  synthetical  methods,  or  reactions,  frequently  blend 
into  one  another.  This  means :  A  reaction  made  with  the  intention 
of  recognizing  a  substance  may  at  the  same  time  produce  some  com- 
pound of  interest  from  a  synthetical  point  of  view. 

Acids.  The  many  compounds  formed  by  the  union  of  elements 
are  so  various  in  their  nature,  that  no  system  of  classification  pro- 
posed up  to  the  present  time  can  be  called  perfect.  There  are,  how- 
ever, a  few  groups  or  classes  of  compounds,  the  properties  of  which 
are  so  well  marked,  that  a  substance  belonging  to  either  of  them  may 
be  easily  recognized.  These  groups  are  the  acids,  bases,  and  neutral 
substances. 

Acids  are  characterized  by  the  following  properties : 

1.  They  have  (when  soluble  in  water)  an  acid  or  sour  taste. 

2.  They  change  the  color  of  many  organic  substances,  for  instance 
of  litmus,  from  blue  to  red. 

3.  They  contain  hydrogen,  which  can  be  replaced  by  metals,  the 
compound  thus  formed  being  a  salt. 

/    According  to  the  number  of  hydrogen  atoms  replaceable  by  metals, 
/  we  distinguish  monobasic,  dibasic,  and  tribasic  acids.     Hydrochloric 
\  acid,  HC1,  is  a  monobasic,  sulphuric  acid,  H2SO4,  is  a  dibasic,  phos- 
phoric acid,  H3PO4,  is  a  tribasic  acid. 

Bases  or  basic  substances  show  properties  which  are  chemically 
opposite  to  those  of  acids.  These  properties  are : 

1.  They  have  (when  soluble  in  water)  the  taste  of  lye,  or  an  alka- 
line taste. 

2.  They  have  (when  soluble  in  water)  an  alkaline  reaction,  i.  e.y 
they  restore  the  color  of  organic  substances  when  previously  changed 
by  a9ids,  for  instance  that  of  litmus,  from  red  to  blue. 

3.  When  acted  upon  by  acids,  they  form  salts.     For  instance: 
Potassium  hydroxide  is  a  base ;  when  brought  in  contact  with  hy- 
drochloric acid  it  forms  water  and  the  salt  potassium  chloride : 

KOH     +    HC1    =    H20     +     KC1. 

Neutral  substances.  All  substances  having  neither  acid  nor  basic 
properties  are  neutral.  Water,  for  instance,  is  a  neutral  substance, 
having  no  acid  or  alkaline  taste,  and  no  action  on  red  or  blue  litmus. 
Many  neutral  substances,  to  some  extent  even  water,  appear  to  possess 


DECOMPOSITION  OF  COMPOUNDS.  59 

the  characteristic  properties  of  both  classes,  acids  and  bases  ;  of  neither 
class,  however,  to  a  very  great  extent. 

Salts.  Salts  are  acids  in  which  hydrogen  has  been  replaced  by 
metals  or  by  basic  radicals;  a  salt  may  be  formed  by  the  union  of  an 
acid  and  a  base  (usually  with  the  simultaneous  formation  of  water), 
or  by  the  action  of  an  acid  on  a  metal  (usually  with  the  liberation  of 
hydrogen). 

For  instance  : 

NaOH        -f        HNO3        =        NaNO3        +        H2O. 
Sodium  Nitric  Sodium  Water. 

hydroxide.  acid.  nitrate. 

Fe  +        H2SO4        =         FeSO4         +        H2. 

Iron.  Sulphuric  Ferrous  Hydrogen. 

acid.  •-  sulphate. 

The  process  of  combining  an  acid  with  a  base  in  such  a  proportion 
that  the  acid  and  alkaline  reactions  disappear,  and  a  neutral  salt  is 
formed,  is  known  as  neutralization. 

According  to  the  number  of  hydrogen  atoms  replaced  in  an  acid, 
we  distinguish  normal  and  acid  salts.  [A  normal  salt  is  one  formed  by 
the  replacement  of  all  the  replaceable  hydrogen  atoms  of  an  acidA 
For  instance:  Potassium  chloride,  KC1,  potassium  sulphate,  K2SO4,  / 
potassium  phosphate,  K3PO4.  (As  monobasic  acids  have  but  one  atom 
of  hydrogen  which  can  be  replaced,  they  form  normal  salts  only.) 

Normal  salts  often  have  a  neutral  reaction  to  litmus,  but  they  may 

have  an  acid,  or  even  an  alkaline  reaction. 

7 

Acid  salts  are  acids  in  which  there  has  been  replaced  only  a  portion 
of  their  replaceable  hydrogen  atoms.  /  For  instance:  KHSO4, 
K2HP04,  KH2P04 

Basic  salts  are  salts  containing  a  higher  proportion  of  a  base  than 
is  necessary  for  the  formation  of  a  normal  salt/  Instances  are  basic 
mercuric  sulphate,  HgSO4.(HgO)2,  basic  lead  nitrate,  Pb(NO3)2. 
Pb(OH)2.  According  to  modern  views  basic  salts  are  looked  upon 
as  derived  from  bases  by  replacement  of  part  of  their  hydrogen  by  acid 
radicals.  In  the  base  lead  hydroxide,  Pb(OH)2,  one  of  the  hydrogen 
atoms  may  be  replaced  by  the  radical  of  nitric  acid,  when  basic  lead 

NO 
nitrate,  Pb       rr3'  is  formed. 


In  bismuth  hydroxide,  Bi(OH)3,  one,  two,  or  three  hydrogen  atoms 
may  be  replaced  by  nitric  acid,  when  the  salts  Bi(^  /QTT\     -^^\OH 

and  Bi(NO3)3  are  formed.     The  first  two  compounds  are  basic  salts, 
while  the  third  one  is  the  normal  salt. 


60  PRINCIPLES  OF  CHEMISTRY. 

Double  salts  are  salts  formed  by  replacement  of  hydrogen  in  an 
(  acid  by  more  than  one  metal.     For  instance :  Potassium-sodium  sul- 
phate, KNaSO4. 

Residue,  radical,  or  compound  radical,  are  expressions  for  un- 
saturated  groups  of  atoms  known  to  enter  as  a  whole  into  different 
compounds,  but  having  no  separate  existence.  For  instance:  The 
bivalent  oxygen  combines  with  two  atoms  of  the  univalent  hydrogen, 
forming  the  saturated  compound  H2O,  water.  If  we  take  from  this 
H2O  one  atom  of  H,  there  is  left  the  group  of  atoms  HO  (now  gener- 
ally written  OH),  consisting  of  an  atom  of  oxygen  in  which  but  one 
point  of  attraction  is  actually  saturated,  the  second  one  not  being 
provided  for. 

This  group,  OH,  is  a  residue  or  radical,  and  is  known  to  enter  into 
many  compounds ;  it  is,  for  instance,  a  constituent  of  all  the  different 
hydroxides  (formerly  called  hydrates),  such  as  potassium  hydroxide, 
KOH,  calcium  hydroxide,  ca(OH)-2,  etc. 

According  to  the  number  of  points  of  attraction  left  unprovided 
for  in  a  radical,  we  distinguish  univalent,  bivalent,  trivalent,  and 
quadrivalent  radicals. 

Carbon  is  a  quadrivalent  element  forming  with  the  univalent  hy- 
drogen the  saturated  compound  CH4.  By  removal  of  one,  two,  or 
three  hydrogen  atoms  the  radicals  CH3',  CH2",  CH//r,  are  formed. 

ENEEAL  EEMAEKS  EEGAEDING  ELEMENTS. 


Relative  importance  of  different  elements.  Of  the  total 
jr  number  of  about  sixty-nine  elements,  comparatively  but  few  (about 
one-fourth)  are  of  great  and  general  importance  for  the  earth,  and  the 
phenomena  taking  place  upon  it.  These  important  elements  form 
the  greater  part  of  the  mass  of  the  solid  portion  of  the  earth,  and  of 
the  water  and  atmosphere,  and  of  all  animal  and  vegetable  matter. 

QUESTIONS.— 71.  What  physical  actions  have  a  tendency  to  decompose  com- 
pound substances  ?  72.  Explain  the  terms  reaction  and  reagent.  73.  Mention 
some  instances  of  decomposition  produced  by  the  action  of  one  substance  upon 
another  substance.  74.  Why  can  no  general  rules  be  established  in  regard  to 
the  amount  of  attraction  which  different  elements  have  for  each  other  ?  75^ 
What  is  the  difference  between  analytical  and  synthetical  methods  ?  76.  Define 
an  acid,  and  state  the  general  properties  of  basic  and  neutral  substances.  By 
what  means  can  they  be  recognized?  77.  Distinguish  between  mono-,  di-,  and 
tri-basic  acids.  78.  What  are  salts  and  how  are  they  formed?  79.  Define 
neutral,  acid,  and  double  salts.  80.  Explain  the  term  radical  or  residue. 


GENERAL  REMARKS  REGARDING  ELEMENTS. 


61 


Another  number  of  elements  are  of  less  importance,  because  either 
they  are  not  found  in  any  large  quantity,  or  do  not  take  any  active 
or  essential  part  in  the  formation  of  organic  matter ;  yet  they  are  of 
interest  and  importance  on  account  of  being  used,  in  their  elementary 
state  or  in  the  form  of  different  compounds,  in  every-day  life  for 
various  purposes. 

A  third  number  of  elements  are  found  in  such  minute  quantities 
in  nature  that  they  are  almost  exclusively  of  scientific  interest.  Even 
the  existence  of  some  elements,  the  discovery  of  which  has  been 
claimed,  is  doubtful. 

The  elements  enumerated  in  column  I.  are  those  of  great  and  gen- 
eral interest ;  in  II.  those  claiming  interest  on  account  of  the  special 
use  made  of  them ;  in  III.  those  having  scientific  interest  only. 

I.  II.  III. 

Aluminum  Antimony  Beryllium  (Glucinum) 

Calcium  Arsenic  Caesium 

Carbon  Barium  Columbium  (Niobium) 

Chlorine  Bismuth  Didymium 

Hydrogen  Boron  Erbium 

Iron  Bromine  Gallium 

Magnesium  Cadmium  Germanium 

Nitrogen  Cerium  Indium 

Oxygen  Chromium  Iridium 

Phosphorus  Cobalt  Lanthanum 

Potassium  Copper  Osmium 

Silicon  Fluorine  Palladium 

Sodium  Gold  Ehodium 

Sulphur  Iodine  Kubidium 

Lead  Ruthenium 

Lithium  Samarium 

Manganese  Scandium 

Mercury  Selenium 

Molybdenum  Tantalum 

Nickel  Tellurium 

Platinum  Terbium 

Silver  Thallium 

Strontium  Thorium 

Tin  Titanium 

Zinc  Tungsten 

Uranium 
Vanadium 
Ytterbium 
Yttrium 
Zirconium 

Classification  of  elements  may  be  based  upon  either  physical  or 
chemical  properties,  or  upon  a  consideration  of  both.  A  natural 


62  PRINCIPLES  OF  CHEMISTRY. 

classification  of  all  elements  is  the  one  dividing  them  into  two  groups 
of  metals  and  non-rnetals. 

^Metals  are  all  elements  which  have  that  peculiar  lustre  known  as 
metallic  lustre  •)  which  are  good  conductors  of  heat  and  electricity; 
which,  in  combination  with  oxygen,  form  compounds  generally 
showing  basic  properties  ;  and  which  are  capable  of  replacing  hy- 
drogen in  acids,  thus  forming  salts. 

Non-metals  or  metalloids  are  all  elements  not  having  the  above- 
mentioned  properties.  Their  oxides  in  combination  with  water  gen- 
erally have  acid  properties.  In  all  other  respects  the  chemical  and 
physical  properties  of  non-metals  differ  widely.  Their  number 
amounts  to  14,  the  other  55  elements  being  metals. 

Natural  groups  of  elements.  Besides  classifying  all  elements 
into  metals  and  non-metals,  certain  members  of  both  classes  exhibit 
so  much  resemblance  in  their  properties,  that  many  of  them  have 
been  arranged  into  natural  groups.  The  members  of  such  a  natural 
group  frequently  show  some  connection  between  atomic  weights  and 
properties. 

Chlorine,      354  Sulphur,       32  Lithium,          7  Calcium,        40 

Bromine,       80  Selenium,     78.8  Sodium,          23  Strontium,     87 

Iodine,        126.5  Tellurium,  125  Potassium,      39  Barium,       137 

Each  three  elements  mentioned  in  the  above  four  columns  resemble 
each  other  in  many  respects,  forming  a  natural  group.  The  relation 
between  the  atomic  weights  will  hardly  be  suspected  by  looking  at 
the  figures,  but  will  be  noticed  at  once  by  adding  together  the  atomic 
weights  of  the  first  and  last  elements  and  dividing  this  sum  by  2, 
when  the  atomic  weights  (very  nearly,  at  least)  of  the  middle  mem- 
bers of  the  series  are  obtained.  Thus  : 


35.4  +  126.5  32  +  125_7g5.    7  +  39_23.  40  +  137__g85 

2222 

Mendelejeff's  periodic  law.1  The  relationship  between  atomic 
weights  and  properties  has  been  used  for  arranging  all  elements  sys- 
tematically in  such  a  manner  that  the  existing  relation  is  clearly 
pointed  out.  Of  the  various  schemes  proposed,  the  one  arranged  by 
Mendelejeff  may  be  selected  as  most  suitable  to  show  this  relation. 

1  The  consideration  of  this  law  should  be  postponed  until  the  student  has  become  acquainted 
with  the  larger  number  of  important  elements. 


GENERAL  REMARKS  REGARDING  ELEMENTS.  ^3 

Looking  at  MendelejefF s  ';able  on  page  64,  it  will  be  seen  that  ail 
the  elements  are  arranged  in  the  order  of  their  atomic  weights,  and 
that  the  latter  increase  gradually  by  only  a  unit  or  a  few  units. 
Moreover,  the  arrangement  is  such  that  eight  groups  and  twelve 
series  are  formed.  The  remarkable  features  of  this  classification 
may  thus  be  stated :  Elements  which  are  more  or  less  closely  allied 
in  their  physical  and  chemical  properties  are  made  to  stand  together 
in  a  group,  as  may  be  seen  by  pointing  out  a  few  of  the  more  gen- 
erally known  instances  as  found  in  the  groups  I.,  II.,  and  VII.,  the 
first  one  containing  the  alkali  metals,  the  second,  the  metals  of  the 
alkaline  earths,  the  last  the  halogens. 

There  is,  moreover,  to  be  noticed  a  periodic  repetition  in  the  prop- 
erties of  the  elements  arranged  in  the  horizontal  lines  from  left  to 
right.  Leaving  out  group  VIII.  for  the  present,  we  find  that  the 
power  of  the  elements  to  combine  with  oxygen  atoms  increases  regu- 
larly from  the  left  to  the  right,  whilst  the  power  of  the  elements  to 
combine  with  hydrogen  atoms  increases  from  the  right  to  left,  as  may 
be  shown  by  the  following  instances  : 

I.  II.  Ill  IV.  V.  VI.  VII. 

Na20  MgO  A12O3  SiO2  P2O5  SO3  C12OT 

Hydrogen  compounds  unknown  SiH^  PH3  SH2  C1H 

The  oxides  on  the  left  show  strongly  basic  properties,  as  illustrated 
by  sodium  oxide  ;  these  basic  properties  become  weaker  in  the  second, 
and  still  weaker  in  the  third  group  ;  the  oxides  of  the  fourth  group 
show  either  indifferent,  or  but  slightly  acid  properties,  which  latter 
increase  gradually  in  the  fifth,  sixth,  and  seventh  groups. 

While  some  elements  show  an  exception,  it  may  be  stated  that 
most  of  the  elements  of  group  I.  are  univalent,  of  II.  bivalent,  of 
III.  trivalent,  of  IV.  quadrivalent,  of  V.  quinquivalent,  of  VI. 
sexivalent,  and  of  VII.  septivalent. 

Properties  other  than  those  above  mentioned  might  be  enumerated 
in  order  to  show  the  regular  gradation  which  exists  between  the 
members  of  the  various  series,  but  what  has  been  pointed  out  will 
suffice  to  prove  that  there  exists  a  regular  gradation  in  the  properties 
of  the  elements  belonging  to  the  same  series,  and  that  the  same  change 
is  repeated  in  the  other  series,  or  that  the  changes  in  the  properties  of 
elements  are  periodic.  It  is  for  this  reason  that  a  series  of  elements 
is  called  a  period  (in  reality  a  small  period,  in  order  to  distinguish  it 
from  a  large  period,  an  explanation  of  which  term  will  be  given 
directly). 

The  12  series  or  periods  given  in  the  following  table  show  another 


PRINCIPLES  OF  CHEMISTRY. 


3 


8 

'     of 


Q 
o 

s 

H 
PH 


•* 

too 


It 


GENERAL  REMARKS  REGARDING  ELEMENTS.  65 

highly  characteristic  feature,  which  consists  in  the  fact  that  the  corre- 
sponding members  of  the  even  (2, 4,  6,  etc.)  periods  and  of  the  uneven 
(3,  5,  7,  etc.)  periods  resemble  each  other  more  closely  than  the  mem- 
bers of  the  even  periods  resemble  those  of  the  uneven  periods.  Thus 
the  metals  calcium,  strontium,  and  barium,  of  the  even  periods,  4,  6, 
and  8,  resemble  each  other  more  closely  than  they  resemble  the  metals 
magnesium,  zinc,  and  cadmium,  of  the  uneven  periods,  3,  5,  and  7,  the 
latter  metals  again  resembling  each  other  greatly  in  many  respects. 

It  is  for  this  reason  that  in  the  table  the  elements  belonging  to  one 
group  are  not  placed  exactly  underneath  each  other,  but  are  divided 
into  two  lines  containing  the  members  of  even  and  uneven  periods 
separately,  whereby  the  elements  resembling  each  other  most  are 
made  to  stand  together. 

In  arranging  the  elements  by  the  method  indicated,  it  was  found 
that  the  elements  mentioned  in  group  VIII.  could  not  be  placed  in 
any  of  the  12  small  periods,  but  that  they  had  to  be  kept  separately 
in  a  group  by  themselves,  three  of  these  metals  always  forming  an 
intermediate  series  following  the  even  periods  4,  6,  and  10. 

An  uneven  and  even  series,  together  with  an  intermediate  series, 
form  a  large  period,  the  number  of  elements  contained  in  a  complete 
large  period  being,  therefore,  7  +  7  +  3  =  17. 

An  apparently  objectionable  feature  is  the  incompleteness  of  the 
table,  many  places  being  left  blank ;  but  it  is  this  very  point  which 
renders  the  table  so  highly  interesting  and  valuable. 

Mendelejeff,  in  arranging  his  scheme,  claimed  that  the  places  left 
blank  belonged  to  elements  not  yet  discovered,  and  he  predicted  not 
only  the  existence  of  these  as  yet  missing  elements,  but  also  described 
their  properties.  Fortunately  his  predictions  have,  in  at  least  three 
cases,  been  verified,  three  of  the  missing  elements  having  since  been 
discovered,  and  named,  scandium,  gallium,  and  germanium.  These 
elements  not  only  fitted  in  the  previously  blank  spaces  by  virtue  of 
their  atomic  weights,  but  their  general  properties  also  assigned  to 
them  the  places  which  they  now  occupy. 

Physical  properties  of  elements.  Most  elements  are,  at  the 
ordinary  temperature,  solid  substances,  two  are  liquids  (bromine  and 
mercury),  five  are  gases  (oxygen,  hydrogen,  nitrogen,  chlorine,  and 
fluorine).  Most  of  the  solid  elements  may  be  converted  into  liquids 
and  gases  by  the  action  of  heat.  Some  solid  elements,  however,  have 
so  far  resisted  all  attempts  to  change  their  state  of  aggregation,  as,  for 
instance,  carbon. 

5 


66  PRINCIPLES  OF  CHEMISTRY. 

Most,  if  not  all,  of  the  solid  elements  may  be  obtained  in  the  crys- 
tallized state;  a  few  are  amorphous  and  crystallized,  or  polymorphous. 
The  physical  properties  of  many  elements  in  these  different  states 
differ  widely.  For  instance :  Carbon  is  known  crystallized  as  diamond 
and  graphite,  or  amorphous  as  charcoal.  The  property  of  elements  to 
assume  such  different  conditions  is  called  allotropy,  and  the  different 
forms  of  an  element  are  termed  attotropic  modifications. 

Some  of  the  gaseous  elements  are  also  capable  of  existing  in  allo- 
tropic  modifications.  For  instance :  Oxygen  is  known  as  such  and  as 
ozone,  the  latter  differing  from  the  common  oxygen  both  in  its  physi- 
cal and  chemical  properties.  The  explanation  given  for  this  surprising 
fact,  that  one  and  the  same  element  has  different  properties  in  certain 
modifications,  is,  that  either  the  molecules  or  the  atoms  within  the 
molecules  are  arranged  differently.  Ozone,  for  instance,  has  thrce- 
atoms  of  oxygen  in  the  molecule,  wliile  the  common  oxygen  molecule 
contains  but  two  atoms. 

Most  of  the  elements  are  tasteless  and  odorless ;  a  few,  however, 
have  a  distinct  odor  and  taste,  as,  for  instance,  iodine  and  bromine. 

Relationship  between  elements  and  the  compounds  formed 
by  their  union.  The  properties  of  the  compounds  formed  by  the 
combination  of  elements  are  so  various  that  it  is  next  to  impossible 
to  give  any  general  rule  by  which  they  may  be  indicated.  It  may 
be  said,  however,  that  nearly  all  of  the  gaseous  compounds  contain 
at  least  one  gaseous  element,  and  that  solid  elements,  when  combining 
with  each  other,  generally  form  solid  substances,  rarely  liquids,  and 
never  compounds  showing  the  gaseous  state  at  the  ordinary  tem- 
perature. 

Nomenclature.  The  chemical  nomenclature  of  compound  sub- 
stances has  undergone  considerable  changes  within  the  last  twenty 
years.  These  changes  were  made  in  conformity  with  our  present 
views  of  the  constitution  of  the  compounds. 

When  two  elements  combine  in  one  proportion  only,  little  difficulty 
is  experienced  in  the  formation  of  a  name,  as,  for  instance,  in  iodide 
of  potassium  or  potassium  iodide,  KI,  chloride  of  sodium  or  sodium 
chloride,  NaCl. 

When  two  elements  combine  in  more  than  one  proportion,  the 
syllables,  mono,  di,  tri,  tetra,  and  penta  are  frequently  used  to  designate 
the  relative  quantity  of  the  elements.  For  instance :  Carbon  mon- 
oxide, CO,  carbon  dioxide,  CO2,  phosphorus  tfn'chloride,  PC13,  phos- 
phorus pentachloiridQ,  PC15. 


GENERAL  REMARKS  REGARDING  ELEMENTS.  67 

In  many  cases  the  syllables  ous  and  io  are  used  to  distinguish  the 
proportions  in  which  two  elements  combine ;  the  syllable  ous  being 
used  for  the  simpler  or  lower,  the  syllable  ie  for  the  more  complex  or 
higher  form  of  combination.  For  instance :  Phosphorous  chloride, 
PC13,  and  phosphoric  chloride,  PC15;  ferrous  oxide,  FeO,  feme 
oxide,  Fe2O3. 

The  syllables  mono  and  sesqui  also  are  used  occasionally  to  mark 
this  difference,  as,  for  instance,  monoxide  of  iron,  FeO,  sesquioxide  of 
iron,  Fe2O3. 

When  two  oxides  of  the  same  element  ending  in  ous  and  ic  form 
acids  (by  entering  in  combination  with  water),  the  same  syllables  are 
used  to  distinguish  these  acids.  Phosphoroits  oxide,  P2O3,  forms 
phosphorous  acid  ;  phosphoric  oxide,  P2O5,  forms  phosphoric  acid. 

The  salts  formed  by  these  acids  are  distinguished  by  using  the 
syllables  ite  and  ate.  Phosphite  of  sodium  is  derived  from  phospho- 
rous acid,  phosphate  of  sodium  from  phosphoric  acid.  Sulphites 
and  sulphates  are  derived  from  sulphurous  and  sulphuric  acid, 
respectively. 

According  to  the  new  nomenclature,  the  name  of  the  metal  precedes 
that  of  the  acid  or  acid  radical  in  an  acid.  For  instance,  sodium 
phosphite,  instead  of  phosphite  of  sodium ;  potassium  sulphate,  instead 
of  sulphate  of  potassium.  The  acids  themselves  are  looked  upon  as 
hydrogen  salts,  and  are  sometimes  named  accordingly  :  hydrogen 
nitrate  for  nitric  acid,  hydrogen  chloride  for  hydrochloric  acid,  etc. 

"When  the  number  of  elements  and  the  number  of  atoms  increase  in 
the  molecule,  the  names  become  in  most  cases  more  complicated.  The 
rules  applied  to  the  formation  of  such  complicated  names  will  be 
spoken  of  later. 

Writing1  chemical  equations.  It  has  been  shown  that  chemical 
changes  are  expressed  in  chemical  equations  by  means  of  symbols. 
These  equations  are  formed  by  placing  the  molecules  which  are  to  act 
upon  one  another,  and  which  are  called  factors  and  are  connected  by 
the  sign  -f,  to  the  left  of  the  sign  of  equality,  and  by  placing  the 
molecule  or  molecules  which  result  from  the  decomposition,  and  are 
called  product  or  products,  to  the  right  of  the  sign  of  equality,  con- 
necting them  also  by  the  +  sign  if  more  than  one  product  be  formed. 

Every  correct  chemical  equation  is  correct  mathematically  also — 
i.  e.y  the  sum  of  the  atoms  as  well  as  that  of  the  molecular  weights  of 
the  factors  equals  the  sum  of  the  atoms  and  that  of  the  molecular 
weights  of  the  products  respectively.  For  instance :  Sodium  car- 


68  PRINCIPLES  OF  CHEMISTRY. 

bonate  and  calcium  chloride  form   calcium    carbonate  and   sodium 
chloride.     Expressed  in  chemical  equation  we  say  : 

Na,COs  +  CaCl2  =  CaCO3  +  2NaCl. 

Sodium  carbonate  and  calcium  chloride  are  the  factors,  calcium  car- 
bonate and  sodium  chloride  the  products.  Adding  together  the 
molecular  weights  of  the  factors  and  those  of  the  products  we  find 
equal  quantities,  as  follows  : 

2Na  =  46          Ca  =  40  Ca  =  40        2Na  =  46 

C   =12         2C1  =  71  C   =12        2C1  =  71 

3O    =48  3O   =48 

106        +       111=217  100       +        117=217 

Chemical  equations  not  only  are  'used  for  representing  chemical 
changes,  but  also  are  the  starting-point  in  all  the  chemical  calcula- 
tions in  which  the  quantities  of  substances  entering  into  chemical 
actions,  or  the  quantities  of  the  product  formed,  are  concerned. 

The  above  calculation  teaches,  for  instance,  that  106  parts  by 
weight  of  sodium  carbonate  are  acted  upon  by  1  1  1  parts  by  weight  of 
calcium  chloride,  and  that  100  parts  by  weight  of  calcium  carbonate 
and  117  parts  by  weight  of  sodium  chloride  are  formed  by  this  action. 
These  data  may,  of  course,  be  utilized  1o  find  how  much  calcium 
chloride  may  be  needed  for  the  decomposition  of  one  pound  or  of  any 
other  definite  weight  of  sodium  carbonate  ;  or  how  much  of  these  two 
substances  may  be  required  to  produce  one  hundred  pounds,  or  any 
other  definite  weight,  of  calcium  carbonate. 

While  in  many  cases  of  chemical  decomposition  the  change  which  is 
to  take  place  cannot  be  foretold,  but  has  to  be  studied  experimentally, 
there  are  other  chemical  changes  which  can  be  predicted  with  certainty 
(see  Chapter  8,  page  56).  In  the  latter  case  especially  there  is  no 
difficulty  in  writing  out  the  change  in  the  form  of  an  equation.  In 
doing  this  it  must  be  borne  in  mind  that  equivalent  quantities  replace  one 
another;  that,  for  instance,  two  atoms  of  a  univalent  element  are 
required  to  replace  one  atom  of  a  bivalent  element,  as,  for  instance,  in 
the  case  of  the  decomposition  taking  place  between  potassium  iodide 
and  mercuric  chloride,  when  two  molecules  of  the  first  are  required  to 
decompose  one  molecule  of  the  second  compound  : 


K  —  I  TTW/C1           TT/I           K  —  Cl 

K  —  I  •    MS\C1  :       ***\I           K  —  Cl 
or 

2KI  +    HgCl2  =    HgI2    +  2KC1. 


GENERAL  REMARKS  REGARDING  ELEMENTS.  69 

Whenever  the  exchange  of  atoms  takes  place  between  univalent 
and  trivalent  elements,  three  of  the  first  are  required  for  one  of  the 
second,  as  in  the  case  of  the  action  of  sodium  hydroxide  on  bismuth 
chloride  : 

Na  —  OH  /Cl  /OH  Na  —  Cl 

Na  —  OH  +    Bi—  Cl    =    Bi—  OH    +    Na  —  Cl 
Na  —  OH  \C1  \OH  Na  —  Cl 

or 

3NaOH  +    BiCl3    =    Bi(OH)3    +    SNaCl. 

In  the  following  examples  of  double  composition  an  exchange 
takes  place  between  the  atoms  of  metallic  elements,  or  between  the 
metallic  elements  and  the  hydrogen.  The  student,  in  completing  the 
equations,  has  also  to  select  the  correct  quantity,  i.  e.y  the  correct 
number  of  molecules  of  the  factors  required  for  the  change.  The 
interrogation  marks  indicate  that  more  than  one  atom  or  one  molecule 
of  the  substance  is  needed  for  the  reaction. 

Na'  +  H'Cl  Cu"SO4         +  H/S 

H/SO4  +  K'(?)  Ba"Cl2  +  Na/SO4 

Ca"  +  H'Cl  (?)      =  Na/CO3        +  H2'SO4 

Fe"  +  H/SO4       ==  Bi"'(NO3)3  +  K'OH  (?)        = 

H'Cl  +  Ag'N08      =  AV"(S04)8  +  K'OH  (?)       = 

Ca"Cl2  +  Ag'N03(?)=  A1/^(S04)3  +  C 

Bi'"Cl3  +  Ag^N03(?)  =  Fe/"Cl6       +  A 


How  to  study  chemistry.  In  studying  chemistry,  the  student 
is  advised  to  impress  upon  his  memory  five  points  regarding  every 
important  element  or  compound.  These  points  are  : 

1.  Occurrence  in  nature.     Whether  in    free  or   combined   state; 
whether  in  the  air,  water,  or  solid  part  of  the  earth. 

2.  Mode  of  preparation  by  artificial  means. 

3.  Physical  properties.     State  of  aggregation  and  influence  of  heat 
upon  it  ;  color,  odor,  taste,  solubility,  etc. 

4.  Chemical  properties.     Atomic  and  molecular  weight  ;  valence  ; 
amount  of  attraction  toward   other  elements  or  compounds;  acid, 
alkaline,  or  neutral  reaction  ;  reactions  by  which  it  may  be  recog- 
nized and  distinguished  from  other  substances. 

5.  Application  and  use  made  of  it  in  every-day  life,  in  the  arts, 
manufactures,  or  medicine. 

Of  the  most  important  elements  and  compounds,  the  history  of 
their  discovery,  and,  occasionally,  some  special  points  of  interest, 
should  be  noticed  also. 

All  students  having  the  facility  for  working  in  a  chemical  labora- 
tory are  strongly  advised  to  make  all  those  experiments  and  reactions 


70  PRINCIPLES  OF  CHEMISTRY. 

which  will  be  mentioned  in  connection  with  the  different  substances 
to  be  considered  in  this  book. 

By  adopting  this  mode  of  studying  chemistry  the  student  will  soon 
acquire  a  fair  knowledge  of  chemical  facts,  yet  he  might  know  little 
of  the  science  of  chemistry.  In  order  to  acquire  this  latter  knowl- 
edge he  should  study  not  only  facts,  but  also  the  relationship  existing 
between  them  and  between  the  laws  governing  the  phenomena  con- 
nected with  these  facts.  It  is  by  this  method  only  that  the  science 
of  chemistry  can  be  successfully  mastered. 

QUESTIONS. — 81.  Why  are  not  all  the  elements  of  equal  importance  ?  82. 
State  the  physical  and  chemical  properties  of  metals.  83.  How  are  metals 
distinguished  from  non-metals  ?  84.  What  relation  often  exists  between  the 
atomic  weights  of  elements  belonging  to  the  same  group  ?  85.  Explain  the 
term  allotropic  modification.  86.  Mention  some  elements  capable  of  existing 
in  allotropic  modifications.  87.  What  relation  exists  between  the  properties 
of  elements  and  the  properties  of  the  compounds  formed  by  their  union  ?  88. 
In  which  cases  are  the  syllables  mono-,  di-,  tri-,  tetra-,  and  penta-  used  in 
chemical  nomenclature?  89.  What  use  is  made  of  the  syllables  ous  and  ic, 
ite  and  ate,  in  distinguishing  compounds  from  each  other?  90.  What  are  the 
principal  features  of  the  periodic  law  ? 


III. 

NON-METALS  AND  THEIR  COMBINATIONS, 


THE  total  number  of  the  non-metals  is  fourteen ;  two  of  them, 
selenium  and  tellurium,  are  of  so  little  importance  that  they  will  be 
but  briefly  considered  in  this  book. 


Symbols,  atomic  weights,  and  derivation  of  names. 


Boron,  B    =    10.9.  From  borax,  the  substance  from  which  boron  was  first 

obtained. 

Bromine,       Br  =    79.8.  From  the  Greek  f3ptifj.oe  (bromos),  stench,  in  allusion  to 

the  intolerable  odor. 

Carbon,          C     =    12.      From  the  Latin  carbo,  coal,  which  is  chiefly  carbon. 

Chlorine,        Cl   =    35.4.  From  the  Greek  x^upds  (chloros),  green,  in  allusion  to  its 

green  color. 

Fluorine,        F    =    19.      From  fluorspar,  the  mineral  calcium  fluoride,  used  as  flux 

(fluo,  to  flow.) 

Hydrogen,     H    =      1.     From  the  Greek  iidup  (hudor),  water,  and  yewdw  (gennao), 

to  generate. 

Iodine,  I     =  126.5.  From  the  Greek  lov  (ion),  violet,  referring  to  the  color  of 

its  vapors. 

Nitrogen,       N    =    14.      From  the  Greek  virpov  (nitron),  nitre,  and  yewdu  (gen- 
nao), to  generate. 

Oxygen,          O    =    16.     From  the  Greek  o?6f  (oxus),  acid,  and  yewdu  (gennao), 

to  generate. 

Phosphorus,?     =    31.     From  the  Greek  0w?  (phos) ,  light,  and  <j>ep£iv  (pherein),  to 

bear. 
Silicon,  Si    =    28.3.  From  the  Latin  silex,  flint,  or  silica,  the  oxide  of  silicon. 

Sulphur,        S     =    32.     From  sal,  salt,  and  irvp  (pur),  fire,  referring  to  the  com- 
bustible properties  of  sulphur. 

(71) 


72  NON-METALS  AND  THEIR  COMBINATIONS. 


State  of  aggregation. 

Under  ordinary  conditions  the  non-metals   show   the   following 
states : 

Oases.  Liquids.  Solids. 

B.  P.  F.  P.  B.  P. 

Hydrogen,  ~\  Are    converted        Bromine,  63°  C.      Phosphorus,    44°  C.      280°  C. 
Oxygen,       v    into  liquids  with  Iodine,  107  175 

Nitrogen,    )    difficulty.  Sulphur,        111  400 

Chlorine,       Easily  liquefied.  Carbon,  ^ 

Fluorine,  ?  Boron,    C  Infusible. 

Silicon,  3 

Occurrence  in  nature. 

a.  In  a  free  or  combined  state. 

Carbon  in  coal,  organic  matter,  carbon  dioxide,  carbonates. 
Nitrogen  in  air,  ammonia,  nitrates,  organic  matter. 
Oxygen  in  air,  water,  organic  matter,  most  minerals. 
Sulphur  chiefly  as  sulphates  and  sulphides. 

b.  In  combination  only. 
Boron  in  boric  acid  and  borax. 

Bromine  in  salt  wells  and  sea- water  as  magnesium  bromide,  etc . 
Chlorine  as  sodium  chloride  in  sea-water,  etc. 
Fluorine  as  calcium  fluoride,  fluorspar. 
Hydrogen  in  water  and  organic  matter. 
Iodine  as  iodides  in  sea-water. 

Phosphorus  as  phosphate  of  calcium,  iron,  etc.,  in  bones  and  rocks. 
Silicon  as  silicic  acid  or  silica,  and  in  silicates. 

Time  of  discovery. 

Sulphur, ")  Long  known  in  the  elementary  state  ;  recognized  as  elements  in  the 

Carbon,   J      latter  part  of  the  eighteenth  century. 

Phosphorus,  1669,  by  Brandt,  of  Germany. 

Chlorine,  1770,  by  Scheele,  of  Sweden. 

Nitrogen,  1772,  by  Kutherford,  of  England. 

Oxygen,  1774,  by  Priestley,  of  England,  and  Scheele,  of  Sweden. 

Hydrogen,  1781,  by  Cavendish,  of  England 

Boron,  1808,  by  Gay-Lussac,  of  France. 

Fluorine,  1810,  by  Ampere,  of  France. 

Iodine,  1812,  by  Courtois,  of  France. 

Silicon,  1823,  by  Berzelius,  of  Sweden. 

Valence. 

Univalent.  Bivalent.  Trivalent  or  quinquivalent.       Quadrivalent. 

Hydrogen,  Oxygen,  Nitrogen,  Carbon, 

Chlorine,  Sulphur.  Boron,  Silicon. 

Bromine,  Phosphorus. 

Iodine, 
Fluorine. 


OXYGEN.  73 

10.    OXYGEN. 
OH  =  16  (15.96). 

History.  Oxygen  was  discovered  in  the  year  1774  by  Priestley,  in 
England,  and  Scheele,  in  Sweden,  independently  of  each  other ;  its 
true  nature  was  soon  afterward  recognized  by  Lavoisier,  of  France, 
who  gave  it  the  name  oxygen,  from  the  two  Greek  words,  bf-vs  (oxus), 
acid,  and  yew&u  (gennao),  to  produce  or  generate.  Oxygen  means, 
consequently,  generator  of  acids. 

Occurrence  in  nature.  There  is  no  other  element  on  our  earth 
present  in  so  large  a  quantity  as  oxygen.  It  has  been  calculated  that 
not  less  than  about  one-third,  possibly  as  much  as  45  per  cent.,  of  the 
total  weight  of  our  earth  is  made  up  of  oxygen ;  it  is  found  in  a  free 
or  uncombined  state  in  the  atmosphere,  of  which  it  forms  about  one- 
fifth  of  the  weight.  Water  contains  eight-ninths  of  its  weight  of 
oxygen,  and  most  of  the  rocks  and  different  mineral  constituents  of 
our  earth  contain  oxygen  in  quantities  varying  from  30  to  50  per 
cent. ;  finally,  it  is  found  as  one  of  the  common  constituents  of  most 
animal  and  vegetable  matters. 

If  the  unknown  interior  of  our  earth  should  be  similar  in  composition  to  the 
solid  crust  of  mineral  constituents  which  have  been  analyzed,  then  the  sub- 
joined table  will  give  approximately  the  proportions  of  those  elements  present 
in  the  largest  quantity. 

Oxygen      .  .  .45  parts.  Calcium  .  .  .4  parts. 

Silicon        .  .  .     28     "  Magnesium  .  .     2     " 

Aluminum  .               8     "  Sodium   .  .  .     2     " 

Iron  .         .  .               6     "  Potassium  .  .     2     " 

Preparation.  The  oxides  of  the  so-called  noble  metals  (gold, 
silver,  mercury,  platinum)  are  by  heat  easily  decomposed  into  the 
metal  and  oxygen : 

HgO=Hg  +  O; 

Ag20=2Ag  +  O. 

A  more  economical  method  of  obtaining  oxygen  is  the  decomposi- 
tion of  potassium  chlorate,  KC1O3,  into  potassium  chloride,  KC1, 
and  oxygen  by  application  of  heat : 

KC1O3  =  KC1  +  30. 

While  the  above  formula  represents  the  final  result  of  the  decomposition,  it 
takes  place  actually  in  two  stages.  At  first  potassium  chlorate  gives  up  but 
one-third  of  its  total  oxygen,  forming  potassium  chloride  and  perchlorate, 

KC104,  thus : 

2KC1O3  b=  KC10,  +  KC1  +  2O. 


74  NON-METALS  AND  THEIR  COMBINATIONS. 

This  part  of  the  decomposition  takes  place  at  a  comparatively  low  temper- 
ature ;  after  it  is  complete,  the  temperature  rises  considerably  and  the  decom- 
position of  the  perchlorate  begins : 

KC1O4  =  KC1  +  40. 

If  the  potassium  chlorate  be  mixed  with  30-50  per  cent,  of  man- 
ganese dioxide,  and  this  mixture  be  heated,  the  liberation  of  oxygen 
takes  place  with  greater  facility  and  at  a  lower  temperature  than  by 
heating  potassium  chlorate  alone.  Apparently,  the  manganese  dioxide 
takes  no  active  part  in  the  decomposition,  as  its  total  amount  is  found 
in  an  unaltered  condition  after  all  potassium  chlorate  has  been  decom- 
posed by  heat.  A  satisfactory  explanation  regarding  this  action  of 
manganese  dioxide  is  yet  wanting. 

A  third  method  is  to  heat  to  redness,  in  an  iron  vessel,  manganese 
dioxide  (MnO2),  which  suffers  then  a  partial  decomposition : 
3MnO2  =  Mn3O4  -f  2O. 

In  this  case  there  is  liberated  but  one-third  of  the  total  amount  of 
oxygen  present,  while  two-thirds  remain  in  combination  with  the 
manganese. 

Other  methods  of  obtaining  oxygen  are :  Decomposition  of  water  by  elec- 
tricity, heating  of  dichromates,  nitrates,  barium  dioxide,  and  other  substances, 
which  evolve  a  portion  of  the  oxygen  contained  in  the  molecules. 

Heating  a  concentrated  solution  of  bleaching  powder  with  a  small  quantity 
of  a  cobalt  salt  (cobaltous  chloride)  furnishes  a  liberal  supply  of  oxygen,  the 
calcium  hypochlorite  of  the  bleaching  powder  being  decomposed  into  calcium 
chloride  and  oxygen : 

Ca(ClO)2  =  CaCl2  +  2O, 

Oxygen  may  be  obtained  at  the  ordinary  temperature  by  adding  water  to  a 
mixture  of  powdered  potassium  ferricyanide  and  barium  dioxide,  and  also  by 
the  decomposition  of  potassium  permanganate  and  hydrogen  dioxide  in  the 
presence  of  dilute  sulphuric  acid. 

Experiment  1.  Generate  oxygen  by  heating  a  small  quantity  (about  5 
grammes)  of  potassium  chlorate  in  a  dry  flask  of  about  100  c.c.  capacity,  to 
which,  by  means  of  a  perforated  cork,  a  bent  glass  tube  has  been  attached, 
which  leads  under  the  surface  of  water  contained  in  a  dish.  (Fig.  6.)  Collect 
the  gas  by  placing  over  the  delivery-tube  large  test-tubes  (or  other  suitable  ves- 
sels) filled  with  water.  Notice  that  a  strip  of  wood,  a  wax  candle,  or  any  other 
substance  which  burns  in  air,  burns  with  greater  energy  in  oxygen,  and  that 
an  extinguished  taper,  on  which  a  spark  yet  remains,  is  rekindled  when  placed 
in  oxygen  gas.  Notice,  also,  the  physical  properties  of  the  gas.  How  many 
c.c.  of  oxygen  can  be  obtained  from  5  grammes  of  potassium  chlorate  ?  1000  c.c. 
of  oxygen  weigh  1.43  grammes. 

The  quantity  of  oxygen  liberated  from  a  given  quantity  of  a  substance  may 
be  easily  calculated  from  the  atomic  and  molecular  weights  of  the  substance 


OXYGEN. 


75 


or  substances  suffering  decomposition.  For  instance :  100  pounds  of  oxygen 
may  be  obtained  from  how  many  pounds  of  potassium  chlorate,  or  from  how 
many  pounds  of  manganese  dioxide  ? 

The  molecular  weight  of  potassium  chlorate  is  found  by  adding  together  the 
weights  of  1  atom  of  potassium  =  39  +  1  atom  of  chlorine  =  35.4  +  3  atoms 
of  oxygen  =  48 ;  total  =  122.4.  Every  122.4  parts  by  weight  of  potassium 

FIG.  6. 


Apparatus  for  generating  oxygen. 

chlorate  liberate  the  weight  of  3  atoms,  or  48  parts  by  weight,  of  oxygen.     If 
48  are  obtained  from  122.4,  100  are  obtained  from  255. 

48  :  122.4  :  :  100  :  x 

x  =  255. 

In  a  similar  manner,  it  will  be  found  that  813.7  pounds  of  manganese  dioxide 
are  necessary  to  produce  100  pounds  of  oxygen.  Mn02  =  54.8  -f  32  =  86.8. 
3MnO2  =  3  X  86.8  =  260.4.  Every  260.4  parts  furnish  2  X  16  =  32  parts  of 
oxygen. 

32  :  260.4  :  :  100  :  x 

x  =  813.7. 

Physical  properties.  Oxygen  is  a  colorless,  inodorous,  tasteless 
gas ;  up  to  a  few  years  ago  it  was  looked  upon  as  a  permanent  or 
stable  gas,  as  all  attempts  to  liquefy  or  solidify  it  had  failed.  Lately, 
however,  these  efforts  have  been  successful,  and  oxygen  has  been  con- 
verted (though  in  small  quantities)  into  a  colorless  liquid  by  the 
application  of  a  pressure  of  470  atmospheres  at  a  temperature  of 
_130°  C.  (—202°  F.) 

Oxygen  is  but  sparingly  soluble  in  water  (about  3  volumes  in  100 
at  common  temperature).  A  litre  of  oxygen  under  760  mm.  pressure, 
and  at  the  temperature  0°  C.  (32°  F.),  weighs  1.4298  grammes. 


76  NON-METALS  AND  THEIR  COMBINATIONS. 

Chemical  properties.  The  principal  feature  of  oxygen  is  its  great 
affinity  for  almost  all  other  elements,  both  metals  and  non-metals  ; 
with  nearly  all  of  which  it  combines  in  a  direct  manner.  The  more 
important  elements  with  which  oxygen  does  not  combine  directly  are  : 
Cl,  Br,  I,  F,  Au?  Ag,  and  Pt;  but  even  with  these  it  combines  in- 
directly, excepting  F. 

The  act  of  combination  between  other  substances  and  oxygen  is 
called  oxidation,  and  the  products  formed,  oxides.  The  large  number 
of  oxides  are  divided  usually  into  three  groups,  and  distinguished  as 
basic  oxides  (sodium  oxide,  Na2O,  calcium  oxide,  CaO),  neutral  oxides 
(water,  H2O,  manganese  dioxide,  MnO2,  lead  dioxide,  PbO2),  and 
acid-forming  or  acidic  oxides,  also  called  anhydrides  (carbon  dioxide, 
CO2,  sulphur  trioxide,  SO3).  Whenever  the  heat  generated  by  oxida- 
tion (or  by  any  other  chemical  action)  is  sufficient  to  cause  the  emis- 
sion of  light,  the  process  is  called  combustion.  Oxygen  is  the  chief 
supporter  of  all  the  ordinary  phenomena  of  combustion.  Substances 
which  burn  in  atmospheric  air  burn  with  greater  facility  in  pure 
oxygen.  This  property  is  taken  advantage  of  to  recognize  and  dis- 
tinguish oxygen  from  most  other  gases.  Processes  of  oxidation  evolv- 
ing no  light  are  called  slow  combustion.  An  instance  of  slow  combus- 
tion is  the  combustion  of  the  different  organic  substances  in  the  living 
animal,  the  oxygen  being  supplied  by  respiration. 

For  a  process  of  oxidation  it  is  not  absolutely  necessary  that  free 
oxygen  be  present.  Many  substances  contain  oxygen  in  such  a  form 
of  combination  that  they  part  with  it  easily  when  brought  in  contact 
with  substances  having  a  greater  affinity  for  it.  Such  substances  are 
called  oxufysj/M^gents,  as,  for  instance,  nitric  acid,  potassium  chlorate, 


pota^siujn_permanganate,  etc. 

In  all  combustions  we  have  at  least  two  substances  acting  chemically  upon 
one  another,  which  substances  are  generally  spoken  of  as  combustible  bodies 
and  supporters  of  combustion.  Illuminating  gas  is  a  combustible  substance, 
and  oxygen  a  supporter  of  combustion  ;  but  these  terms  are  only  relatively 
correct,  since  oxygen  may  be  caused  to  burn  in  illuminating  gas,  whereby  it  is 
made  to  assume  the  position  of  a  combustible  substance,  whilst  illuminating 
gas  is  the  supporter  of  combustion. 

While  some  substances,  such  as  iron  and  phosphorus,  undergo  slow  combus- 
tion at  the  ordinary  temperature,  there  is  a  certain  degree  of  temperature, 
characteristic  of  each  substance,  at  which  it  inflames.  This  point  is  known  as 
kindling  temperature,  and  varies  widely  in  different  substances.  Zinc  ethyl 
ignites  at  the  ordinary  temperature,  phosphorus  at  50°  C.  (122°  F.),  sulphur  at 
about  450°  C.  (842°  F.),  carbon  at  a  red  heat,  and  iron  at  a  white  heat.  The 
heat  produced  by  the  combustion  is  generally  higher  than  the  kindling  tern- 


OXYGEN.  77 

perature,  and  it  is  for  this  reason  that  a  substance  continues  to  burn  until  it  is 
consumed,  provided  the  supply  of  oxygen  be  not  cut  off,  and  the  temperature 
be  not  through  some  cause  lowered  below  the  kindling  temperature. 

The  total  amount  of  heat  evolved  during  the  combustion  of  a  substance  is 
the  same  as  that  generated  by  the  same  substance  when  undergoing  slow  com- 
bustion, but  the  intensity  depends  upon  the  time  required  for  the  oxidation. 
A  piece  of  iron  may  require  years  to  combine  with  oxygen,  and  it  may  be 
burned  up  in  a  few  minutes ;  yet  the  total  heat  generated  in  both  cases  is  the 
same,  though  we  can  notice  and  measure  it  in  the  first  instance  by  most  deli- 
cate instruments  only,  while  in  the  second  it  is  very  intense. 

Ozone  is  an  allotropic  modification  of  oxygen,  which  is  formed 
when  non-luminous  electric  discharges  pass  through  atmospheric  air 
or  through  oxygen  ;  when  phosphorus,  partially  covered  with  water, 
is  exposed  to  air,  and  also  during  a  number  of  chemical  decomposi- 
tions. Ozone  differs  from  ordinary  oxygen  by  possessing  a  peculiar 
odor,  by  being  an  even  stronger  oxidizing  agent  than  common  oxygen, 
by  liberating  iodine  from  potassium  iodide,  etc.  This  latter  action 
may  be  used  for  demonstrating  the  presence  of  ozone  by  suspending 
in  the  gas  a  paper  moistened  with  a  solution  of  potassium  iodide  and 
starch.  The  iodine,  liberated  by  the  ozone,  forms  with  starch  a  dark- 
blue  compound.  Theoretically,  we  assume  that  ozone  contains  three, 
common  oxygen  but  two,  atoms  in  the  molecule,  which  is  substan- 
tiated by  the  fact  that  three  volumes  suffer  a  condensation  to  two 
volumes  when  converted  into  ozone,  which  would  indicate  that  three 
molecules  of  oxygen  furnish  two  molecules  of  ozone,  thus : 

302       =       203 
or 

0=0 

O— O 

O=O     = 

O 

O=O  /\ 

O— O 

Ozone  occurs  in  small  quantities  in  country  air,  but  is  rarely  noticed 
in  cities,  where  it  is  decomposed  too  quickly  by  the  impurities  of  the 
atmospheric  air.  It  has  been  assumed  that  ozone  acts  advantageously, 
as  it  has  a  tendency  to  destroy  matters  which  are  unwholesome.  Too 
little,  however,  is  known  of  the  subject  to  justify  a  positive  opinion 
in  regard  to  it. 

QUESTIONS.— 91.  By  whom  and  at  what  time  was  oxygen  discovered?  92. 
How  is  oxygen  found  in  nature  ?  93.  Mention  three  processes  by  which  oxygen 
may  be  obtained.  94.  How  much  oxygen  may  be  obtained  from  490  grammes 
of  potassium  chlorate?  95.  State  the  physical  and  chemical  properties  of 


78  NON-METALS  AND  THEIR  COMBINATIONS. 

11.    HYDKOGEN. 
H  =  l. 

History.  Hydrogen  was  obtained  by  Paracelsus  in  the  16th  cen- 
tury; its  elementary  nature  was  recognized  by  Cavendish,  in  1766. 
The  name  is  derived  from  Mup  (hudor),  water,  and  yew&u  (gennao),  to 
generate,  in  allusion  to  the  formation  of  water  by  the  combustion  of 
hydrogen. 

Occurrence  in  nature.  Hydrogen  is  found  chiefly  as  a  component 
element  of  water ;  it  enters  into  the  composition  of  most  animal  and 
vegetable  substances,  and  is  a  constituent  of  all  acids.  Small  quanti- 
ties of  free  hydrogen  are  found  in  the  gases  produced  by  the  decom- 
position of  organic  matters  (as,  for  instance,  in  the  intestinal  gases), 
and  also  in  the  natural  gas  escaping  from  the  interior  of  the  earth. 

Preparation.  Hydrogen  may  be  obtained  by  passing  an  electric 
current  through  water  previously  acidified  with  sulphuric  acid,  by 
which  it  is  decomposed  into  its  elements^"" 

H2O  =  2H  +  O. 

A  second  process  is  the  decomposition  of  water  by  metals.  Some 
metals,  such  as  potassium  and  sodium,  decompose  water  at  the  ordi- 
nary temperature ;  whilst  others,  iron,  for  instance,  decompose  it  at  a 

red  heat : 

K    +  H2O  =  KOH  +    H ; 
Fe  +  H2O  =  FeO     +  2H. 

A  very  convenient  way  of  liberating  hydrogen  is  the  decomposition 
of  dilute  hydrochloric  or  sulphuric  acid  by  zinc  or  iron  : 

Zn  +  2HC1      =  ZnCl2  +  2H ; 

Zinc 
chloride. 

Fe  +  H2SO4  =  FeSO4  +  2H. 
Ferrous 
sulphate. 

Hydrogen  may  also  be  obtained  by  heating  granulated  zinc  or 

oxygen.  96.  Explain  the  terms  combustion,  slow  combustion,  combustible 
substance,  and  supporter  of  combustion.  97.  Mention  some  oxidizing  agents. 
98.  What  is  ozone,  and  how  does  it  differ  from  common  oxygen?  99.  Under 
what  circumstances  is  ozone  formed?  100.  State  the  molecular  weight  of 
oxygen  and  ozone. 


HYDROGEN.  79 

aluminum  with  strong  solutions  of  potassium  or  sodium  hydroxide, 
in  which  case  the  decomposition  is  explained  thus : 

Zn  +  2KOH    ==;  K2ZnO2    +  2H; 
Potassium 
zincate. 

Al  +  SNaOH  =  Na3AlO3  +  3H. 

Sodium 
aluminate. 

Whenever  hydrogen  is  generated,  care  should  be  taken  to  expel  all 
atmospheric  air  from  the  vessel  in  which  the  generation  takes  place, 
before  the  hydrogen  is  ignited,  as  otherwise  an  explosion  may  result. 

Experiment  2.  Place  a  few  pieces  of  granulated  zinc  (about  10  grammes)  in 
a  flask  of  about  200  c.c.  capacity,  which  is  arranged  as  shown  in  Fig.  7.  Cover 
the  zinc  with  water,  and  pour  upon  it  through  the  funnel  tube  a  little  sulphuric 
acid,  adding  more  when  gas  ceases  to  be  evolved.  Notice  the  effervescence 
around  the  zinc.  Collect  the  gas  in  test-tubes  over  water  and  ignite  it  by  taking 
the  test-tube  (with  mouth  downward)  to  a  flame  near  by.  Notice  that  the  first 
portions  of  gas  collected,  which  are  a  mixture  of  hydrogen  and  atmospheric 
air,  explode  when  ignited  in  the  test-tube,  while  the  subsequent  portions  burn 
quietly.  Pour  the  contents  of  one  test-tube  into  another  one  by  allowing  the 
light  hydrogen  gas  to  rise  into  and  replace  the  air  in  a  test-tube  held  over  the 
one  filled  with  hydrogen.  Take  two  test-tubes  completely  filled  with  the  gas ; 
hold  one  mouth  upward,  the  other  one  mouth  downward :  notice  that  from  the 
first  one  the  gas  escapes  after  a  few  seconds,  while  it  remains  in  the  second 
tube  a  few  minutes,  as  may  be  shown  by  holding  the  tubes  near  a  flame  to 
cause  ignition. 

FIG.  7. 


Apparatus  for  generating  hydrogen. 


After  having  ascertained  that  all  atmospheric  air  has  been  expelled  from  the 
flask,  the  gas  may  be  ignited  directly  at  the  mouth  of  the  delivery  tube,  after 
moving  it  out  of  the  water. 

Experiment  3.  Pour  into  a  test-tube  of  not  less  than  50  c.c.  capacity,  5  c.c.  of 
hydrochloric  acid,  fill  up  with  water,  close  the  tube  with  the  thumb  and  set  it 


80  NON-METALS  AND  THEIR  COMBINATIONS. 

inverted  into  a  porcelain  dish  partly  filled  with  water.  Weigh  of  metallic 
zinc  0.04  gramme,  and  bring  it  quickly  under  the  mouth  of  the  test-tube,  so 
that  the  generated  hydrogen  rises  in  the  tube.  Prepare  a  second  tube  in  the 
same  manner,  and  introduce  0.04  gramme  of  metallic  magnesium.  In  case  the 
decomposition  of  the  acids  by  the  metals  should  proceed  too  slowly,  a  little 
more  acid  may  be  poured  into  the  dishes. 

When  the  metals  are  completely  dissolved  it  will  be  seen  that  the  volumes 
of  hydrogen  in  the  two  tubes  bear  a  relation  to  each  other  of  about  10  to  27. 

In  order  to  measure  the  gas  volumes  as  correctly  as  the  simple  apparatus 
permits,  the  tubes  should  be  transferred  to  a  large  beaker  filled  with  cold  water, 
bringing  the  surfaces  of  the  liquids  in  the  test-tube  and  beaker  on  a  level,  and 
marking  on  the  outside  of  the  test-tubes  (with  a  file  or  paper  strip)  the  exact 
height  of  the  gas. 

After  having  emptied  the  test-tubes,  they  may  be  filled  with  water  from  a 
pipette  or  from  a  burette  to  the  point  which  has  been  marked,  and  thus  the 
exact  volume  of  gas  generated  is  ascertained. 

Repeat  the  operation,  using  0.065  gramme  of  zinc  and  0.024  gramme  of  mag- 
nesium. Notice  that  in  this  case  equal  volumes  of  hydrogen  are  obtained. 
Calculate  the  weight  of  hydrogen  from  the  cubic  centimetres  liberated,  and 
compare  this  weight  with  the  weights  of  zinc  and  magnesium  used.  What 
relation  is  there  between  the  weights  of  the  liberated  hydrogen  and  the  metals 
used,  and  the  atomic  weights  of  these  three  elements  ? 

Properties.  Hydrogen  is  a  colorless,  inodorous,  tasteless  gas ;  it 
is  the  lightest  of  all  known  substances,  having  a  specific  gravity  of 
0.0692  as  compared  with  atmospheric  air  (=  1).  One  litre  of  hydro- 
gen at  0°  C.  (32°  F.),  and  a  barometric  pressure  of  760  ram.,  weighs 
0.0896  gramme,  or  one  gramme  occupies  a  space  of  11.163  litres; 
100  cubic  inches  weigh  about  2.265  grains. 

Hydrogen  resists  liquefaction  more  than  any  other  gas.  When 
subjected  to  a  pressure  of  650  atmospheres  and  a  temperature  of 
— 150°  C.  (—238°  F.),  hydrogen  forms  a  steel-blue  liquid,  a  portion 
of  which  is  converted  into  a  solid  on  suddenly  releasing  the  pressure, 
in  consequence  of  the  intense  cold  produced  by  the  rapid  evapori- 
zation  of  the  liquefied  hydrogen. 

In  its  chemical  properties,  hydrogen  resembles  the  metals  more  than 
the  non-metals ;  it  burns  easily  in  atmospheric  air,  or  in  pure  oxygen, 
with  a  non-luminous,  colorless,  or  slightly  bluish  flame  producing 
during  this  process  of  combustion  a  higher  temperature  than  can  be 
obtained  by  the  combustion  of  an  equal  weight  of  any  other  substance. 

H2  +  O  =  H20. 

The  formation  of  water  by  the  combustion  of  hydrogen  distinguishes 
it  from  other  gases. 

Two  volumes  of  hydrogen  combine  with  one  volume  of  oxygen, 
forming  two  volumes  of  gaseous  water. 


HYDROGEN.  81 

Water,  H2O  =  18.  Hydrogen  monoxide.  Water  is  not  found 
in  nature  in  an  absolutely  pure  state.  The  purest  natural  water  is 
rain-water  collected  after  the  air  has  been  purified  from  dust,  etc.,  by 
previous  rain.  Comparatively  pure  water  may  be  obtained  by 
melting  ice,  since,  when  wrater  containing  impurities  is  frozen  par- 
tially, these  are  mostly  left  in  the  uncongealed  water. 

The  waters  of  springs,  wells,  rivers,  etc.,  differ  widely  from  each 
other ;  they  all  contain  more  or  less  of  substances  dissolved  by  the 
water  in  its  course  through  the  atmosphere  or  through  the  soil  and 
rocks.  The  constituents  thus  absorbed  by  the  water  are  either  solids 
or  gases. 

Solids  generally  found  in  natural  waters  are  common  salt  (sodium 
chloride),  gypsum  (calcium  sulphate),  and  carbonate  of  lime  (calcium 
carbonate)  ;  frequently  found  are  chlorides  and  sulphates  of  potassium 
and  magnesium,  traces  of  silica  and  salts  of  iron.  Gases  absorbed 
by  water  are  constituents  of  the  atmospheric  air,  chiefly  oxygen, 
nitrogen,  and  carbon  dioxide.  One  hundred  volumes  of  water  con- 
tain about  two  volumes  of  nitrogen,  one  volume  of  oxygen,  and  one 
volume  of  carbon  dioxide. 

Mineral  waters  are  spring  waters  containing  one  or  more  sub- 
stances in  such  quantities  that  they  impart  to  the  water  a  peculiar 
taste  and  generally  a  decided  medicinal  action.  According  to  the 
predominating  constituents  we  distinguish  bitter  waters,  containing 
larger  quantities  of  magnesium  salts ;  iron  or  chalybeate  waters, 
containing  carbonate  or  sulphate  of  iron ;  sulphur  or  hepatic  waters, 
containing  hydrogen  sulphide ;  effervescent  waters,  containing  large 
quantities  of  carbonic  acid,  etc. 

Drinking-water.  A  good  drinking-water  should  be  free  from 
color,  odor,  and  taste  ;  it  should  neither  be  an  absolutely  pure  water, 
nor  a  water  containing  too  much  of  foreign  matter.  Water  containing 
from  2  to  4  parts  of  total  inorganic  solids  (chiefly  carbonate  of  lime 
and  common  salt)  in  10,000  parts  of  water  and  about  1  volume  of 
carbon  dioxide  in  100  volumes  of  water,  may  be  said  to  be  a  good 
drinking-water.  There  are,  however,  good  drinking-waters  which 
contain  more  of  total  solids  than  the  amount  mentioned  above. 

Most  objectionable  in  drinking-water  are  organic  substances)  espe- 
cially when  derived  from  animal  matter,  and  more  especially  when 
in  a  state  of  decomposition,  because  such  decomposing  organic  matter 
is  frequently  accompanied  by  living  organisms  (germs)  which  may 

6 

I 


82  NON-METALS  AND  THEIR  COMBINATIONS. 

cause  disease.  Boiling  of  water  destroys  these  germs,  and  by  subse- 
quent filtering  of  the  boiled  water  through  sand,  charcoal,  spongy 
iron,  etc.,  an  otherwise  unwholesome  water  may  be  rendered  fit  for 
drinking. 

It  should  be  remembered  that  no  filter  can  remain  efficient  for  any 
length  of  time,  as  the  impurities  of  the  water  are  retained  by  the 
materials  used  as  a  filter,  and  this  may  become,  therefore,  a  source  of 
pollution  instead  of  a  purifier.  By  heating  to  a  low  red  heat  the 
materials  used  for  filtering,  these  are  cleaned  and  may  be  used  again. 
The  methods  applied  to  the  analysis  of  drinking-water  will  be  men- 
tioned later.  (See  Index.) 

Distilled  water,  Aqua  destillata.  The  process  for  obtaining 
pure  water  is  distillation  in  a  suitable  apparatus.  From  1000  parts 
of  water  used  for  distillation,  the  first  100  parts  distilled  over  should 
not  be  used,  as  they  contain  the  gaseous  constituents.  The  solids, 
contained  in  the  water  are  left  in  the  undistilled  portion,  which  should 
not  be  less  than  200  parts. 

Properties  of  water.  Water  is  an  inodorous,  tasteless,  and,  in 
small  quantities,  colorless  liquid.  Thick  layers  of  water  show  a  blue 
color.  It  is  perfectly  neutral,  yet  it  has  a  tendency  to  combine  with 
both  acid  and  basic  substances.  These  compounds  are  usually  called 
hydroxides  (formerly  hydrates),  such  as  NaOH,  Ca(OH)2,  etc.  These 
compounds  are  often  formed  by  direct  union  of  an  oxide  with  water, 

thus  : 

CaO  -f  H2O  =  Ca(OH)2. 

Water  is  the  most  common  solvent,  both  in  nature  and  in  artificial 
processes.  As  a  general  rule,  solids  are  dissolved  more  quickly  and 
in  larger  quantities  by  hot  water  than  by  cold,  but  to  this  there  are 
many  exceptions.  For  instance :  Common  salt  is  nearly  as  soluble 
in  cold  as  in  hot  water ;  sodium  sulphate  is  most  soluble  in  water  of 
33°  C.  (91°  F.),  and  some  calcium  salts  are  less  soluble  in  hot  than 
in  cold  water. 

Many  salts  combine  with  water  in  crystallizing ;  crystallized  sodium 
sulphate,  for  instance,  contains  more  than  half  its  weight  of  water. 
This  water  is  called  water  of  crystallization,  and  is  expelled  generally 
at  a  temperature  of  100°  C.  (212°F.).  Some  crystallized  substances 
lose  water  of  crystallization  when  exposed  to  the  air ;  this  property  is 
known  as  efflorescence.  Crystals  of  sodium  carbonate,  ferrous  sulphate, 
etc.,  effloresce,  as  is  shown  by  the  formation  of  powder  upon  the  crys- 
talline surface.  The  term  deliquescence  is  applied  to  the  power  of 


HYDROGEN.  83 

certain  solid  substances  to  absorb  moisture  from  the  air,  thereby 
becoming  damp  or  even  liquid,  as,  for  instance,  potassium  hydroxide, 
calcium  chloride,  etc.  Such  substances  are  spoken  of  also  as  being 
hygroscopic,  and  are  used  for  drying  gases. 

Hydrogen  dioxide,  Hydrogen  peroxide,  H2O2.     This  compound  T» 
may  be  obtained  in  aqueous  solution  by  the  action  of  carbonic  acid 
(or  other  acids)  on  barium  dioxide  suspended  in  water,  when  barium 
carbonate  and  hydrogen  dioxide  are  formed  : 

BaO2  +  H2O  +  CO2  =  BaCO3  +  H2O2. 

The  liquid,  separated  by  decantation  from  the  insoluble  carbonate, 
may  be  concentrated  under  the  receiver  of  an  air-pump,  and  is,  when 
thus  obtained,  a  colorless  liquid  of  a  specific  gravity  1.45,  possessing 
remarkable  bleaching  and  antiseptic  properties.  By  higher  temper- 
atures, as  well  as  by  the  action  of  many  substances,  it  is  readily  de- 
composed into  water  and  oxygen. 

Solution  of  hydrogen  dioxide,  Aqua  hydrogen!!  dioxidi  is 
made  according  to  the  U.  S.  P.  by  adding  to  barium  dioxide  sus- 
pended in  water  of  a  temperature  not  above  10°  C.  (50°  F.),  diluted 
phosphoric  acid  until  the  reaction,  which  is  first  alkaline,  has  become 
neutral.  Insoluble  barium  phosphate  is  formed,  which  is  removed 
by  filtration.  From  the  clear  filtrate  traces  of  barium  yet  remaining 
in  solution  are  precipitated  by  the  addition  of  a  few  drops  of  sul- 
phuric acid.  The  filtered  solution  is  then  diluted  until  it  contains 
about  3  per  cent.,  by  weight,  of  pure  dioxide,  corresponding  to  about 
10  volumes  of  available  oxygen  in  1  volume  of  the  solution. 

The  solution  is  colorless  and  without  odor,  and  has  a  slight  acid 
reaction  due  to  a  trace  of  free  sulphuric  acid  present ;  it  is  liable  to 
deteriorate  by  age,  especially  on  exposure  to  heat  and  light. 

Glycozone  is  hydrogen  dioxide  dissolved  in  glycerin  instead  of  in 
water. 

Hydrogen  dioxide  may  be  recognized  by  the  following  reactions : 

1 .  Silver  oxide  causes  the  decomposition  of  hydrogen  dioxide  with 
evolution  of  oxygen,  metallic  silver  and  water  being  formed  at  the 

same  time : 

Ag20  +  H202  =  2Ag  +  20  +  H20. 

2.  Mixed  solutions  of  ferric  chloride  and  potassium  ferricyanide 
(which  should  have  no  blue  tinge)  assume  an  intense  blue  color  on 
addition  of  even  a  very  small  quantity  of  hydrogen  peroxide. 


- 


> 


84  NON-METALS  AND  THEIR  COMBINATIONS. 

3.  Solution  of  potassium  permanganate,  acidified  with  sulphuric 
acid,  is  readily  decolorized  with  evolution  of  oxygen : 

5H2O2  +  2KMnO4  +  3H2SO4  =  8H2O  +  2MnSO4  -f  K2SO4  +  10  O. 

This  reaction  is  made  use  of  in  the  volumetric  analysis  of  hydrogen 
dioxide.     (See  Chapter  37.) 

12.    NITROGEN. 

Nili  =  14  (14.01). 

Occurrence  in  nature.  By  far  the  larger  quantity  of  nitrogen  is 
found  in  the  atmosphere  in  a  free  state.  Compounds  containing 
nitrogen  are  chiefly  the  nitrates,  ammonia,  and  many  organic  sub- 
stances. 

Preparation.  Nitrogen  is  obtained  usually  from  atmospheric  air 
by  the  removal  of  its  oxygen.  This  may  be  accomplished  by  burn- 
ing a  piece  of  phosphorus  in  a  confined  portion  of  air,  when  phos- 
phoric oxide,  a  white  solid  substance,  is  formed,  whilst  nitrogen  is  left 
in  an  almost  pure  state. 

Other  methods  for  obtaining  nitrogen  are  by  heating  a  mixture  of 
potassium  nitrite  and  ammonium  chloride  dissolved  in  water : 

KNO2  +  NH4C1  =  KC1  +  2H2O  +  2N; 
Potassium    Ammonium 
nitrite.         chloride. 

or  by  heating  ammonium  nitrite  in  a  glass  retort : 
NH4NO2  =  2H20  +  2K 

Experiment  4.  Use  an  apparatus  as  shown  in  Fig.  6,  page  75.  Place  in  the 
flask  about  10  grammes  of  potassium  nitrite  and  nearly  the  same  amount  of 
ammonium  chloride ;  add  enough  water  to  dissolve  the  salts,  and  apply  heat, 
which  is  to  be  carefully  regulated  from  the  time  the  decomposition  begins,  as 
the  evolution  of  gas  may  otherwise  become  too  rapid.  Collect  the  gas,  and 
notice  its  properties  mentioned  below. 

QUESTIONS. — 101.  Mention  two  processes  by  which  hydrogen  may  be  ob- 
tained. 102.  Show  by  symbols  the  decomposition  of  water  by  potassium,  and 
of  sulphuric  acid  by  iron.  103.  State  the  chemical  and  physical  properties  of 
hydrogen.  104.  How  many  pounds  of  zinc  are  required  to  liberate  100  pounds 
of  hydrogen  ?  105.  State  the  composition  of  water  in  parts  by  weight  and  by 
volume.  106.  Mention  the  most  common  solid  and  gaseous  constituents  of 
natural  waters.  107.  How  does  a  mineral  water  differ  from  other  waters? 
Mention  some  different  kinds  of  mineral  waters  and  their  chief  constituents. 
108.  What  are  the  characteristics  of  a  good  drinking-water?  109.  What  are 
the  purest  natural  waters,  and  by  what  process  may  chemically  pure  water  be 
obtained?  110.  State  composition,  mode  of  manufacture,  and  properties  of 
hydrogen  dioxide. 


NITROGEN.  85 

Properties.  Nitrogen  is  a  colorless,  inodorous,  tasteless  gas; 
which,  at  a  temperature  of —130°  C.  (—202°  F.)  and  a  pressure  of 
280  atmospheres,  may  be  condensed  to  a  colorless  liquid.  It  is  neither, 
like  oxygen,  a  supporter  of  combustion,  nor,  like  hydrogen,  a  com- 
bustible substance ;  in  fact,  nitrogen  is  distinguished  by  having  very 
little  affinity Jor_anypther  element,  and  it  scarcely  enters  directly  into 
combination  with  any  subsFa~nce.  Nitrogen  is  not  poisonous,  yet  not 
being  a  supporter  of  combustion  it  cannot  sustain  animal  life. 
Nitrogen  is  trivalent  in  some  compounds,  quinquivalent  in  others.  .>>  f\ 

Atmospheric  air  is  a  mixture  of  about  four-fifths  of  nitrogen  and 
one-fifth  of  oxygen,  with  small  quantities  of  aqueous  vapor,  carbon 
dioxide,  and  ammonia,  containing  frequently  also  traces  of  nitrous  or 
nitric  acid  and  occasionally  hydrogen  sulphide,  sulphur  dioxide,  and 
hydro-carbons.  Besides  these  gases  there  are  always  suspended  in  the 
air  solid  particles  of  dust  and  very  minute  cells  of  either  animal  or 
vegetable  origin. 

100  volumes  of  atmospheric  air  contain  of 

Oxygen 20.61  volumes. 

Nitrogen 77.95        " 

Carbon  dioxide        .....       0.04        " 
Aqueous  vapor        ....         0  5-1.40        " 
Ammonia    \ 
Nitric  acid  t 

An  analysis  of  air  may  be  made  by  the  following  method :  A  graduated  glass 
tube,  containing  a  measured  volume  of  air,  is  placed  with  the  open  end  down- 
ward into  a  dish  containing  mercury.  A  small  piece  of  phosphorus  is  then 
introduced  and  allowed  to  remain  in  contact  with  the  air  for  several  hours, 
when  it  gradually  combines  with  the  oxygen.  The  remaining  volume  of  air  is 
chiefly  nitrogen,  the  loss  in  volume  represents  oxygen. 

For  the  determination  of  carbon  dioxide  and  water,  a  measured  volume  of 
air  is  passed  through  two  U-shaped  glass  tubes.  One  of  these  tubes  has  previ- 
ously been  filled  with  pieces  of  calcium,  chloride,  the  other  tube  with  pieces  of 
potassium  hydroxide,  and  both  tubes  have  been  weighed  separately.  In  pass- 
ing the  measured  air  through  these  tubes  the  first  one  will  retain  all  the 
moisture,  the  second  one  all  the  carbon  dioxide ;  the  increase  in  weight  of  the 
tubes  at  the  end  of  the  operation  will  give  the  amounts  of  the  two  constituents. 

That  oxygen  is  found  in  the  atmosphere  in  a  free  state  is  explained 
by  the  fact  that  all  elements  having  affinity  for  oxygen  have  entered 
into  combination  with  it,  whilst  the  excess  is  left  uncombined.  Nitro- 
gen is  found  uncombined,  because  it  has  so  little  affinity  for  other 
elements. 


86 


NON-METALS  AND  THEIR  COMBINATIONS. 


Ammonia,  NH3=  17.  This  compound  is  constantly  forming  in 
nature  by  the  decomposition  of  organic  (chiefly  animal)  matter,  such 
as  meat,  urine,  blood,  etc.  It  is  also  obtained  during  the  process  of 
destructive  distillation,  which  is  the  heating  of  non-volatile  organic 
substances  in  suitable  vessels  to  such  an  extent  that  decomposition 
takes  place,  the  generated  volatile  products  being  collected  in  re- 
ceivers. The  manufacture  of  illuminating  gas  is  such  a  process  of 
destructive  distillation ;  coal  is  heated  in  retorts,  and  most  of  the 
nitrogen  contained  in  the  coal  is  converted  into  and  liberated  as 
ammonia  gas,  which  is  absorbed  in  water,  through  which  the  gas  is 
made  to  pass. 


Apparatus  for  generating  ammonia. 

Another  method  of  obtaining  ammonia  is  through  decomposition 
of  ammonium  salts  by  the  hydroxides  of  sodium,  potassium,  or  cal- 
cium. Usually  ammonium  chloride  is  mixed  with  calcium  hydroxide 
and  heated,  when  calcium  chloride,  water,  and  ammonia  are  formed : 

2(NH4C1)  +  Ca(OH)2  =  CaCl2  +  2H2O  +  2NH3. 


NITROGEN.  87 

Experiment  5.  Mix  about  equal  weights  (10  grammes  of  each)  of  ammonium 
chloride  and  calcium  hydroxide  (slaked  lime)  in  a  flask  of  about  200  c.c.  capa- 
city, and  arranged  as  in  Fig.  8 ;  cover  the  mixture  with  water  and  apply  heat. 
As  long  as  any  atmospheric  air  remains  in  the  apparatus,  bubbles  of  it  will 
pass  through  the  water  contained  in  the  cylinder;  afterward  all  gas  will  be 
readily  and  completely  absorbed  by  the  water.  Notice  the  odor  and  alkaline 
reaction  on  litmus  of  the  ammonia  water  thus  obtained.  When  the  gas  is 
being  freely  liberated,  move  the  tube  upward,  as  shown  in  B,  and  collect  the 
gas  by  upward  displacement  in  a  cylinder  or  tube,  which  when  filled  with  gas 
is  held  mouth  downward  into  water,  which  will  rapidly  rise  in  the  tube  by 
absorption  of  the  gas.  Notice  that  ammonia  is  not  readily  combustible,  by 
applying  a  flame  to  the  gas  escaping  from  the  delivery  tube. 

Ammonia  is  a  colorless  gas,  of  a  very  pungent  odor,  an  alkaline 
taste,  and  a  strong  alkaline  reaction.  In  pure  oxygen  it  burns,  form- 
ing water  and  free  nitrogen. 

By  the  mere  application  of  a  pressure  of  seven  atmospheres  or  by 
intense  cold  ( — 40°  C.,  — 40°  F.),  ammonia  may  be  converted  into  a 
liquid,  which  at  — 80°  C.  ( — 112°  F.)  forms  a  solid  crystalline  mass. 
Water  dissolves  about  700  times  its  volume  of  ammonia  gas,  forming 
ammonium  hydroxide  : 

NH3  +  H2O  =  NH4OH. 

For  analytical  reactions  of  ammonia,  see  Ammonium  compounds. 

"Water  of  ammonia,  Aqua  ammonise  (Spirit  of  hartshorn).  This 
is  a  solution  of  ammonia  gas  in  water  or  ammonium  hydroxide  in 
water.  The  common  water  of  ammonia  contains  10  per  cent,  by 
weight  of  ammonia,  and  has  a  specific  gravity  of  0.96  ;  the  stronger 
water  of  ammonia,  aqua  ammonice  fortior,  contains  28  per  cent.,  and 
has  a  specific  gravity  of  0.901.  Ammonia  water  has  the  odor,  taste, 
and  reaction  which  characterize  the  gas. 

Compounds  of  nitrogen  and  oxygen.  Five  distinct  compounds 
of  nitrogen  and  oxygen  are  known.  They  are  named  and  constituted 
as  follows : 

Composition. 

By  weight.  By  volume. 

NO  NO 

Nitrogen  monoxide,  N2O       ...  28  16  2            1 

Nitrogen  dioxide,  N2O2  =  2(NO)  .        .  28  32  2            2 

.    Nitrogen  trioxide,  N2O3         ...  28  48  2            3 

Nitrogen  tetroxide,  N2O4  =  2(NO2)       .  28  64  24 

Nitrogen  pentoxide,  N2O5      ...  28  80  2            5 

The  first,  third,  and  fifth  of  these  compounds  are  capable  of  com- 
bining with  water  to  form  acids,  known  as  hyponitrous,  nitrous,  and 
nitric  acid,  respectively. 


88  NON-METALS  AND  THEIR  COMBINATIONS. 

The  gaseous  compounds  N2O2  and  N2O4  exist  as  such  at  low  temperatures 
only,  and  readily  split  up  at  a  high  temperature  into  the  compounds  NO  and  NO2. 
This  splitting  up  of  molecules  is  known  as  dissociation.  The  terms  nitrogen 
dioxide  and  nitrogen  tetroxide  should  be  applied  only  to  the  compounds  N2O2 
and  N2O4,  but  they  are  used  also  for  the  products  of  dissociation  NO  and  NO2. 

When  electric  sparks  pass  through  atmospheric  air  some  ozone  is  generated 
which  oxidizes  nitrogen,  forming  first  the  lower  and  then  also  the  higher 
oxides ;  these  combine  with  water  to  form  nitrous  and  nitric  acid,  which  acids 
are  taken  up  by  the  ammonia  present  in  the  air,  forming  the  respective 
ammonium  salts. 

Nitrogen  monoxide,  N2O=44.  (Sometimes  called  nitrous  oxide; 
also  laughing  gas).  This  compound  was  discovered  by  Priestley  in 
1776;  its  anaesthetic  properties  were  first  noticed  in  1800  by  Sir 
Humphrey  Davy,  and  it  was  first  used  in  dentistry  by  Dr.  Howard 
Wells,  a  dentist  of  Hartford,  Conn.,  in  1844.  It  may  be  easily 
obtained  by  heating  ammonium  nitrate  in  a  flask  at  a  temperature 
not  exceeding  250°  C.  (482°  F.),  when  the  salt  is  decomposed  into 
nitrogen  monoxide  and  water : 

NH4NO3  =  2H2O  +  N20. 

When  nitrous  oxide  is  prepared  for  use  as  an  anaesthetic  it  should 
be  passed  through  two  wash-bottles  containing  caustic  soda  and  ferrous 
sulphate  respectively ;  these  agents  will  retain  any  impurities  that  may 
be  formed  during  the  decomposition,  especially  from  an  impure  salt. 

Experiment  6.  Use  apparatus  as  represented  in  Fig.  6,  page  75.  Place  in  the 
dry  flask  about  10  grammes  of  ammonium  nitrate,  apply  heat,  collect  the  gas 
in  cylinders  over  water,  and  verify  by  experiments  and  observations  the  correct- 
ness of  the  statements  below  regarding  the  physical  and  chemical  properties 
of  nitrogen  monoxide. 

Nitrogen  monoxide  is  a  colorless,  almost  inodorous  gas,  of  dis- 
tinctly sweet  taste.  It  supports  combustion  almost  as  energetically 
as  oxygen,  but  differs  from  this  element  by  its  solubility  in  cold  water, 
which  absorbs  nearly  its  own  volume.  Under  a  pressure  of  about 
50  atmospheres  it  condenses  to  a  colorless  liquid,  the  boiling-point  of 
which  is  at  about  — 80°  C.  ( — 112°  F.)  and  the  freezing-point  at 
_100°  C.  (—148°  F.) 

When  inhaled  it  causes  exhilaration,  intoxication,  anaesthesia,  and 
finally  asphyxia.  The  gas  is  used  in  dentistry  as  an  anaesthetic,  the 
liquefied  compound  being  sold  for  this  purpose  in  wrought-iron 
cylinders. 

Nitrogen  dioxide,  NO=3O.  This  is  a  colorless  gas  which  is 
formed  generally  when  nitric  acid  acts  upon  metals  or  upon  sub- 


NITROGEN.  89 

stances  which  deoxidize  it.  It  is  capable  of  combining  directly  with 
one  or  more  atoms  of  oxygen,  thereby  forming  NO2,  nitrogen  tetroxide, 
which  is  a  gas  of  deep  red  color  and  poisonous  properties.  Nitrogen 
trioxide  is  of  no  practical  interest. 

Experiment  7.  Pour  about  1  c.c.  of  nitric  acid  upon  a  few  fragments  of 
metallic  copper,  and  apply  heat.  Notice  that  red  fumes  escape,  which  are 
nitrogen  tetroxide,  and  that  a  blue  solution  is  formed  which  contains  cupric 
nitrate.  See  explanation  of  the  change  below. 

Hyponitrous  acid,  HNO,  and  nitrous  acid,  HNO2,  have  not  been 
isolated  and  are  known  in  combination  only.  Nitrous  acid  and 
nitrites  occur,  in  small  quantity,  in  air,  and  also  in  water,  where 
they  are  formed  by  decomposition  of  nitrogenous  organic  matter. 

Nitrites  evolve  red  fumes  on  the  addition  of  sulphuric  acid  ;  they  act  as 
reducing  agents  decolorizing  acidified  solution  of  potassium  permanganate; 
they  color  blue  a  mixture  of  zinc  iodide  and  starch  solution  ;  they  give  a  dark- 
brown  color  with  solution  of  meta-phenylene-diamine,  C6H4(NH2)2,  in  the 
presence  of  free  sulphuric  acid. 

Nitric  acid,  Acidum  nitricum,  HNO3—  63  (Aqua  fortis,  Hydric 
nitrate).  Nitrogen  pentoxide,  N2O5,  a  white,  solid,  unstable  com- 
pound, is  of  scientific  interest  only.  When  brought  in  contact  with 
water  it  readily  combines  with  it,  forming  nitric  acid  : 

N2O5  +  H2O  =  2HNO3. 

The  usual  method  for  obtaining  nitric  acid  is  the  decomposition  of 
sodium  nitrate  by  sulphuric  acid  : 


NaN03  4-  H2SO4  =    HNO3  +  HNaSO,; 

Sodium 
bisulphate. 

or 

2NaN03  +  H2SO4  ==  2HNO3  +  Na2SO4. 

Sodium 
sulphate. 

Experiment  8.  Prepare  an  apparatus  as  shown  in  Fig.  9.  Heat  in  a  retort  of 
about  250  c.c.  capacity  a  mixture  of  about  50  grammes  of  potassium  nitrate 
and  nearly  the  same  weight  of  sulphuric  acid.  Nitric  acid  is  evolved  and  distils 
over  into  the  receiver,  which  is  to  be  kept  cool  during  the  operation  by  pouring 
cold  water  upon  it  or  by  surrounding  it  with  pieces  of  ice.  Examine  the 
properties  of  nitric  acid  thus  made,  and  use  it  for  the  tests  mentioned  below. 
How  much  pure  nitric  acid  can  be  obtained  from  50  grammes  of  potassium 
nitrate  ?  Weigh  the  acid  which  you  obtain  in  the  experiment  and  compare 
this  weight  with  the  theoretical  quantity. 

The  acid  thus  obtained  is  an  almost  colorless,  fuming,  corrosive 
liquid,  of  a  peculiar,  somewhat  suffocating  odor,  and  a  strongly  acid 


90 


NON-METALS  AND  THEIR  COMBINATIONS. 


reaction.  When  exposed  to  sunlight  it  assumes  a  yellow  or  yellowish- 
red  color  in  consequence  of  its  decomposition  into  nitrogen  tetroxide, 
water,  and  oxygen. 

Common  nitric  acid,  of  a  specific  gravity  1.414,  is  composed  of  68 
per  cent,  of  HNO3  and  32  per  cent,  of  water.  The  diluted  nitric  acid 
of  the  U.  S.  P.  is  made  by  mixing  ten  parts  by  weight  of  the  common 
acid  with  fifty-eight  parts  of  water,  and  contains  10  per  cent,  of  abso- 
lute nitric  acid;  it  has  a  specific  gravity  of  1.057. 

Fuming  nitric  acid  has  a  brown-red  color,  due  to  nitrogen  tetroxide, 
and  emits  vapors  of  the  same  color.  Specific  gravity  1.45  to  1.50. 

FIG.  9. 


Distillation  of  nitric  acid. 

Mtric  acid  is  completely  volatilized  by  heat;  it  stains  animal 
matter  distinctly  yellow ;  it  is  a  monobasic  acid  forming  salts  called 
nitrates.  These  salts  are  all  soluble  in  water,  for  which  reason  nitric 
acid  cannot  be  precipitated  by  any  reagent.  Nitric  acid  is  a  strong 
oxidizing  agent ;  this  means  that  it  is  capable  of  giving  off  part  of 
its  oxygen  to  substances  having  affinity  for  it. 

The  action  of  nitric  acid  upon  such  metals  as  copper,  silver,  and  many  others 
involves  two  changes,  viz. :  displacement  of  the  hydrogen  of  the  acid  by  the 
metal : 

Cu  +  2HM)3  =  Cu(N03)2  +  2H ; 

and  the  deoxidation  of  another  portion  of  nitric  acid  by  the  liberated  hydrogen 
while  yet  in  the  nascent  state.    Thus  : 

HNO3  +  3H  =  2H2O  +  NO. 

The  liberated  nitrogen  dioxide,  which  is  colorless,  readily  absorbs  oxygen 
from  the  air,  forming  red  vapors  of  nitrogen  tetroxide. 


NITROGEN.  91 

Tests  for  nitric  acid  or  nitrates. 
(Potassium  nitrate,  KNO3,  may  be  used  as  a  nitrate.) 

1.  Nitric  acid  when  heated  with  copper  filings,  or  nitrates  when 
heated  with  copper  filings  and  sulphuric  acid,  evolve  red  fumes  of 
nitrogen  tetroxide.     (See  explanation  above.)     On  the  addition  of 
alcohol  to  the  mixture,  the  odor  of  nitrous  ether  is  noticed. 

2.  The  solution  of  a  nitrate,  to  which  a  few  small  pieces  of  ferrous 
sulphate  have  been  added,  will  show  a  reddish-purple  or  black  color- 
ation upon  pouring  a  few  drops  of  strong  sulphuric  acid  down  the 
side  of  the  test-tube,  so  that  it  may  form  a  layer  at  the  bottom  of  the 
tube.     The  black  color  is  due  to  the  formation  of  an  unstable  com- 
pound of  the  composition  2FeSO4.NO. 

3.  Solution  of  indigo  is  changed  to  yellow  by  nitric  acid.     Solu- 
tions of  nitrates  mixed   with  dilute  sulphuric  acid  do  not  bleach 
indigo  in  the  cold,  but  do  so  on  heating. 

4.  Nitrates  deflagrate  when  heated  on  charcoal  by  means  of  the 
blowpipe. 

5.  When  a  few  drops  of  a  solution  of  1  part  of  brucine  in  300 
parts  of  5  per  cent,  dilute  sulphuric  acid  are  added  to  a  very  dilute 
solution  of  a  nitrate,  and  then  some  concentrated  sulphuric  acid  is 
carefully  poured  down  the  side  of  the  test-tube,  a  red  color,  changing 
to  yellow,  is  produced  at  the  line  of  contact. 

6.  When  a  few  drops  of  solution  of  diphenylamine,  NH(C6H5)2,  in 
concentrated  sulphuric  acid  are  added  to  solution  of  a  nitrate,  and 
then  concentrated  sulphuric  acid  is  poured  down  the  side  of  the  test- 
tube,  a  deep-blue  color  is  formed  at  the  line  of  contact. 

7.  Crystals  of  pyrogallic  acid,  C6H3(OH)3,  added  to  solution  of  a 
nitrate,  and  then  concentrated  sulphuric  acid  poured  down  the  side 
of  the  test-tube,  produce  a  deep-brown  color  at  the  line  of  contact. 

Reactions  5,  6,  and  7  show  1  part  of  nitric  acid  in  one,  three,  and 
ten  million  parts  of  water  respectively,  and  are  used  chiefly  to  detect 
traces  of  nitric  acid  in  drinking-water.  As  sulphuric  acid  may  con- 
tain nitric  acid,  the  tests  should  also  be  made  with  the  sulphuric  acid 
alone  in  order  to  prove  its  purity. 

As  an  antidote  in  cases  of  poisoning  by  nitric  acid  a  solution  of  sodium  car- 
bonate, or  a  mixture  of  magnesia  and  water,  may  be  administered  with  the 
view  of  neutralizing  the  acid. 

QUESTIONS. — 111.  State  the  physical  and  chemical  properties  of  nitrogen. 
112.  Mention  the  principal  constituents  of  atmospheric  air  and  the  quantity  in 
which  they  are  present.  113.  By  what  processes  can  the  four  chief  constituents 


92  NON-METALS  AND  THEIR  COMBINATIONS. 

13.     CARBON. 

Civ  =  12  (11.97). 

Occurrence  in  nature.  Carbon  is  a  constituent  of  all  organic 
matter.  In  a  pure  state  it  is  found  crystallized  as  diamond  and 
graphite,  amorphous  in  a  more  or  less  pure  condition  in  the  various 
kinds  of  coal,  charcoal,  boneblack,  lampblack,  etc.  As  carbon 
dioxide,  carbon  is  found  in  the  air;  as  carbonic  acid,  in  water;  as 
carbonates  (marble,  limestone,  etc.),  in  the  solid  portion  of  our  earth. 

Properties.  The  three  different  allotropic  modifications  of  carbon 
differ  widely  from  each  other  in  their  physical  properties. 

Diamond  is  the  purest  form  of  carbon,  in  which  it  is  crystallized  in 
regular  octahedrons,  cubes,  or  in  some  figure  geometrically  connected 
with  these.  Diamond  is  the  hardest  substance  known ;  it  is  infusible, 
but  burns  when  heated  intensely,  forming  carbon  dioxide. 

Graphite,  plumbago,  or  black-lead,  is  carbon  crystallized  in  short 
six-sided  prisms;  it  is  a  somewhat  rare,  dark -gray  mineral,  chiefly 
used  for  lead- pencils. 

Amorphous  carbon  is  a  soft,  black,  solid  substance. 

Neither  form,  of  carbon  is  fusible,  volatile,  or  soluble  in  any  of  the 
common  solvents. 

Carbon  is  a  quadrivalent  element ;  it  has  little  affinity  for  metals, 
but  combines  with  many  of  the  non-metals,  chiefly  with  oxygen, 
hydrogen,  and  nitrogen,  forming  organic  substances. 

Tests  for  carbon. 

1.  Most    non-volatile    (organic)    substances    containing    carbon, 
blacken  when  heated  on  platinum  foil.     Starch  or  sugar  may  be  used 
for  this  test. 

2.  The  product  of  combustion  of  carbon  (or  of  combustible  matter 
containing  it),  CO2,  renders  lime-water  turbid,  in  consequence  of  the 
formation  of  insoluble  calcium  carbonate,  CaCO3. 

of  atmospheric  air  be  determined?  114.  Mention  some  decompositions  by 
which  ammonia  is  generated.  115.  Explain  the  process  of  making  water  of 
ammonia.  116.  State  the  physical  and  chemical  properties  of  ammonia  gas 
and  ammonia  water.  117.  How  is  nitrogen  monoxide  obtained,  and  what  are 
its  properties  ?  118.  Describe  the  process  for  making  nitric  acid,  and  give 
symbols  for  decomposition.  119.  How  does  nitric  acid  act  on  animal  matter, 
and  what  are  its  properties  generally?  120.  Give  tests  and  antidote  for  nitric 
acid. 


CARBON,  93 

Carbon  dioxide,  CO2  =  44.  (Formerly  named  carbonic  acid,  or 
anhydrous  carbonic  acid.)  This  compound  is  always  formed  during 
the  combustion  of  carbon  or  of  organic  matter ;  also  during  the  decay 
(slow  combustion),  fermentation,  and  putrefaction  (processes  of  decom- 
position) of  organic  matter ;  it  is  constantly  produced  in  the  animal 
system,  exhaled  from  the  lungs,  and  given  off  through  the  skin. 
Many  spring  waters  contain  considerable  quantities  of  the  gas,  one 
single  spring  in  Nauheim,  Germany,  liberating  as  much  as  3000 
pounds  of  carbon  dioxide  a  day. 

By  heating,  many  carbonates  are  decomposed  into  oxides  of  the 
metals  and  carbon  dioxide. 

Lime-burning  is  such  a  process  of  decomposition  : 

CaCO3  =  CaO  -f  CO2. 
Calcium      Calcium 
carbonate,      oxide. 

Another  method  for  the  generation  of  carbon  dioxide  is  the  decom- 
position of  any  carbonate  by  an  acid  : 

CaCO3    +    2HC1  =  CaCl2  +  H2O  +  CO2. 
Calcium     Hydrochloric   Calcium 
carbonate.          acid.          chloride. 

Experiment  9.  Use  apparatus  represented  in  Fig.  7,  page  79.  Place  about 
20  grammes  of  marble,  CaCo3,  in  small  pieces  (sodium  carbonate  or  any  other 
carbonate  may  be  used)  in  the  flask,  cover  it  with  water,  and  add  hydrochloric 
acid  through  the  funnel-tube.  The  escaping  gas  may  be  collected  over  water, 
as  in  the  case  of  hydrogen,  or  by  downward  displacement,  i.  e.,  by  passing  the 
delivery -tube  to  the  bottom  of  a  tube  or  other  suitable  vessel,  when  the  carbon 
dioxide,  on  account  of  its  being  heavier  than  atmospheric  air,  gradually  dis- 
places the  latter.  This  will  be  shown  by  examining  the  contents  of  the  vessel 
with  a  burning  paper,  which  is  extinguished  as  soon  as  most  of  the  air  has 
been  expelled. 

Examine  the  gas  for  its  high  specific  gravity,  by  pouring  it  from  one  vessel 
into  another ;  for  its  power  of  extinguishing  flames,  by  mixing  it  with  an  equal 
volume  of  air,  which  mixture  will  be  found  not  to  support  the  combustion  of 
a  taper  notwithstanding  that  oxygen  is  contained  in  it.  Add  to  one  portion  of 
the  collected  gas  some  lime-water,  shake  it,  and  notice  that  it  becomes  turbid. 
Blow  air  exhaled  from  the  lungs  through  a  glass  tube  into  lime-water,  and 
notice  that  it  also  turns  turbid. 

Carbon  dioxide  is  a  colorless,  odorless  gas,  having  a  faintly  acid 
taste.  By  a  pressure  of  38  atmospheres,  at  a  temperature  of  0°  C. 
(32°  F.),  carbon  dioxide  is  converted  into  a  colorless  liquid,  which  by 
intense  cold  ( — 79°  C.,  — 110°  F.)  may  be  converted  into  a  white, 
solid,  crystal!  ine,  snow-like  substance.  The  specific  gravity  of  carbon 
dioxide  is  1.524;  it  is  consequently  about  one-half  heavier  than 
atmospheric  air. 


94  NON-METALS  AND  THEIR  COMBINATIONS. 

Cold  water  absorbs  at  the  ordinary  pressure  about  its  own  volume 
of  carbon  dioxide,  and  much  larger  quantities  under  an  increased 
pressure  (soda  water). 

Carbon  dioxide  is  not  combustible,  and  not  a  supporter  of  combus- 
tion ;  on  the  contrary,  it  has  a  decided  tendency  to  extinguish  flames, 
air  containing  one-tenth  of  its  volume  of  carbon  dioxide  being  unable 
to  support  the  combustion  of  a  candle.  Whilst  not  poisonous  when 
taken  into  the  stomach,  carbon  dioxide  acts  indirectly  as  a  poison 
when  inhaled,  because  it  cannot  support  respiration,  and  prevents, 
moreover,  the  proper  exchange  between  the  carbon  dioxide  of  the 
blood  and  the  oxygen  of  the  atmospheric  air. 

Common  atmospheric  air  contains  about  4  volumes  of  carbon 
dioxide  in  10,000  of  air,  or  0.04  per  cent.  In  the  process  of  respira- 
tion this  air  is  inhaled,  and  a  portion  of  the  oxygen  is  absorbed  in 
the  lungs  by  the  blood,  which  conveys  it  to  the  different  portions  of  the 
animal  body,  and  receives  in  exchange  for  the  oxygen  a  quantity  of 
carbon  dioxide,  produced  by  the  union  of  a  former  supply  of  oxygen 
with  the  carbon  of  the  different  organs  to  which  the  blood  is  supplied. 

The  air  issuing  from  the  lungs  contains  this  carbon  dioxide,  in 
quantity  about  4  volumes  in  100  of  exhaled  air,  which  is  100  times 
more  than  contained  in  fresh  air. 

Exhaled  air  is,  moreover,  contaminated  by  other  substances  than  carbon 
dioxide,  such  as  ammonia,  hydrocarbons,  and  most  likely  traces  of  other  or- 
ganic bodies,  the  true  nature  of  which  has  not  been  fully  recognized,  but  which 
seem  to  be  directly  poisonous.  The  bad  effects  experienced  in  breathing  air 
which  has  become  contaminated  by  the  exhalations  from  the  lungs,  are  most 
likely  due  to  these  unknown  bodies.  As  we  have  as  yet  no  methods  of  ascer- 
taining the  quantity  of  these  poisonous  substances  present  in  exhaled  air,  the 
determination  of  the  amount  of  exhaled  carbon  dioxide  present  must  serve  as 
an  indicator  of  the  fitness  of  an  air  for  breathing  purposes.  As  a  general  rule, 
it  may  be  stated  that  it  is  not  advisable  to  breathe,  for  any  length  of  time,  air 
containing  more  than  0.1  per  cent,  of  exhaled  carbon  dioxide ;  in  air  contain- 
ing 0.5  per  cent,  most  persons  are  attacked  by  headache,  still  larger  quantities1 
produce  insensibility,  and  air  containing  8  per  cent,  of  carbon  dioxide  causes 
death  in  a  few  minutes. 

As  exhaled  air  contains  from  3.5  to  4  per  cent,  of  carbon  dioxide,  it  is  unfit 
to  be  breathed  again.  The  total  amount  of  carbon  dioxide  evolved  by  the 
lungs  and  skin  of  a  grown  person  amounts  to  about  0.7  cubic  foot  per  hour. 
Hence  the  necessity  for  a  constant  supply  of  fresh  air  by  ventilation.  This 
becomes  the  more  necessary  where  an  additional  quantity  of  carbon  dioxide  is 
supplied  by  illuminating  flames. 

Mentioned  above  are  many  processes  by  which  carbon  dioxide  is 
constantly  produced  in  nature,  and  we  might  assume  that  the  amount 


CARBON.  95 

of  0.04  per  cent,  of  carbon  dioxide  contained  in  atmospheric  air 
would  gradually  increase.  This,  however,  is  not  the  case,  because 
plants,  and  more  especially  all  their  green  parts,  are  capable  of  ab- 
sorbing carbon  dioxide  from  the  air,  whilst  at  the  same  time  they 
liberate  oxygen. 

This  process  of  vegetable  respiration  (if  we  may  so  call  it),  which 
takes  place  under  the  influence  of  sunlight,  is,  consequently,  the 
reverse  of  that  of  animal  respiration.  The  animal  uses  oxygen  and 
liberates  carbon  dioxide ;  the  plant  consumes  this  carbon  dioxide  and 
liberates  oxygen. 

Carbon  dioxide  is  an  acid  oxide,  which  combines  with  water,  form- 
ing carbonic  acid  : 

CO2  +  H2O  =  H2CO3. 

Carbonic  acid,  H2CO3,  is  not  known  in  a  pure  state,  but  always 
diluted  with  much  water,  as  in  all  the  different  natural  waters.  Car- 
bonic acid  is  a  bibasic,  extremely  weak  acid,  the  salts  of  which  are 
known  as  carbonates.  Many  of  these  carbonates  (calcium  carbonate, 
for  instance)  are  abundantly  found  in  nature. 

Tests  for  carbon  dioxide,  carbonic  acid,  and  carbonates. 

(Sodium  carbonate,  Na2CO3,  may  be  used  ) 

1.  Pass  carbon  dioxide  through  lime-water,  which  is  rendered 
turbid  by  the  formation  of  calcium  carbonate : 

Ca(OH)2  -f  C02  =  CaC03  +  H2O. 

2.  From  carbonates,  evolve  the  gas  by  the  addition  of  some  acid, 
and  examine  it  by  the  same  method. 

3.  The  soluble  carbonates  of  potassium,  sodium,  and  ammonium, 
give  precipitates  with  the  solutions  of  most  metallic  salts ;  for  instance, 
with  the  chlorides  of  Ba,  Ca,  Sr,  Mg,  Fe,  Zn,  Cu,  etc. 

Carbon  monoxide,  carbonic  oxide,  CO  =  28.  Carbon  mon- 
oxide is  a  colorless,  odorless,  tasteless,  neutral  gas,  almost  insoluble 
in  water ;  it  burns  with  a  pale-blue  flame,  forming  carbon  dioxide ; 
it  is  very  poisonous  when  inhaled,  forming  with  the  coloring  matter 
of  the  blood  a  compound  which  prevents  the  absorption  of  oxygen. 
Carbon  monoxide  is  formed  when  carbon  dioxide  is  passed  over  red- 
hot  coal. 

CO2  -|-  C  =  2CO. 

The  conditions  necessary  for  the  formation  of  carbon  monoxide  are, 
consequently,  present  in  any  stove  or  furnace  where  coal  burns  with 


96    '  NON-METALS  AND  THEIR  COMBINATIONS. 

an  insufficient  supply  of  air.  The  carbon  dioxide  formed  in  the  lower 
parts  of  the  furnace  is  decomposed  by  the  coal  above.  The  blue 
flames  frequently  playing  over  a  coal  fire  are  burning  carbon  mon- 
oxide. This  gas  is  formed  also  by  the  decomposition  of  oxalic  acid 
(and  many  other  organic  substances)  by  sulphuric  acid  : 


H2C204    +    H2S04  ==  H2SO4.H2O  +  CO2  +  CO. 
Oxalic  Sulphuric 

acid.  acid. 

Carbon  monoxide  is  now  manufactured  on  a  large  scale  by  causing 
the  decomposition  of  steam  by  coal  heated  to  red  heat.  The  decom- 
position takes  place  thus  : 

H2O    +    C    :  :    2H    -f    CO. 

The  gas  mixture,  thus  obtained  and  known  as  water-gas,  may  be  used 
for  heating  purposes  directly,  but  has  to  be  mixed  with  hydrocarbons 
when  used  as  an  illuminating  agent,  for  reasons  which  will  be  pointed 
out  below  when  considering  the  nature  of  flames. 

Compounds  of  carbon  and  hydrogen.  There  are  no  other  two 
elements  which  are  capable  of  forming  so  large  a  number  of  different 
combinations  as  are  carbon  and  hydrogen.  Several  hundred  of  these 
hydrocarbons  are  known,  and  their  consideration  belongs  to  the 
domain  of  organic  chemistry. 

Two  of  these  hydrocarbons,  however,  may  be  briefly  mentioned, 
as  they  are  of  importance  in  the  consideration  of  common  flames. 
These  compounds  are  :  methane  (marsh-gas,  fire-damp),  CH4  ;  and 
eihene  (olefiant  gas),  C2H4. 

Both  compounds  are  colorless,  almost  odorless  gases,  and  both  are 
products  of  the  destructive  distillation  of  organic  substances.  De- 
structive distillation  is  the  heating  of  non-volatile  organic  substances 
in  such  a  manner  that  the  oxygen  of  the  atmospheric  air  has  no  access, 
and  to  such  an  extent  that  the  molecules  of  the  organic  matter  are 
split  up  into  simpler  compounds.  Among  the  gaseous  products 
formed  by  this  operation,  more  or  less  of  the  two  hydrocarbons 
mentioned  above  is  found. 

Marsh-gas  is  formed  frequently  by  the  decomposition  of  organic 
matter  in  the  presence  of  moisture  (leaves,  etc.,  in  swamps)  ;  and  dur- 
ing the  formation  of  coal  in  the  interior  of  the  earth  the  gas  often 
gives  rise  to  explosion  in  coal  mines.  During  these  explosions  of  the 
methane  (mixed  with  air  and  other  gases),  called  fire-damp  by  the 
miners,  carbon  is  converted  into  carbon  dioxide,  which  the  miners 
speak  of  as  choke-damp,  or  after-damp. 


CARBON. 


1  97 


FIG.  10. 


Flame  is  gas  in  the  act  of  combustion.  Of  combustible  gases, 
have  been  mentioned :  hydrogen,  carbon  monoxide,  marsh-gas,  and 
olefiant  gas.  These  four  gases  are  actually  those  which  are  found 
chiefly  in  any  of  the  common  flames  produced  by  the  combustion  of 
organic  matter,  such  as  paper,  wood,  oil,  wax,  or  illuminating  gas  itself. 

These  gases  are  generated  by  destructive  distillation,  the  heat  being 
supplied  either  by  a  separate  process  (manufacture  of  illuminating 
gas  by  heating  wood  or  coal  in  retorts),  or  generated  during  the 
combustion  itself. 

In  burning  a  candle,  for  instance,  fat  is  constantly  decomposed  by 
the  heat  of  the  flame  itself,  the  generated  gases  burning  continuously 
until  all  fat  has  been  decomposed,  and  the  products  of 
decomposition  have  been  burned  up,  i.  e.,  have  been 
converted  into  carbon  dioxide  and  water. 

An  ordinary  flame  (Fig.  10)  consists  of  three__rjarjbs 
or  cones.  The  inner  or  central  portion  is  chiefly  un- 
burnt  gas;  the  second  is  formed  of  partially  burnt  and 
burning  gas;  the  outer  cone,  showing  the  highest  tem- 
perature, but  scarcely  any  light,  is  that  part  of  the  flame 
where  complete  combustion  takesj)lace. 

I      The  light  of  a  flame  is  caused  by  solid  particles  of  ) 
carbon  heated  to  a  white  heat.    The  separation  of  carbon/ 
in  the  flame  is  explained  by  the  fact  that  hydrogen  has 
a  greater  affinity  for  oxygen  than  has  carbon ;  only  a 
limited  amount  of  oxygen  can  penetrate  into  the  flame, 
and  the  hydrogen  of  the  hydrocarbon  will  consume  this 
oxygen,  the  carbon  being  liberated  momentarily  until  it 
reaches  the  outer  cone,  where  it  finds  sufficient  oxygen  with  which  to 

combine. 

jt 

If  a  sufficient  amount  of  air  be  previously  mixed  with  the  illumi- 
'nating  gas,  as  is  done  in  the  Bunsen  burner,  no  separation  of  carbon 
takes  place,  and,  therefore,  no  light  is  produced,  but  a  more  intense 
heat  is  generated. 

Silicon  or  Silicium,  Si  =  28.3,  is  found  in  nature  very  abun- 
dantly as  silicon  dioxide,  or  silica,  SiO2  (rock-crystal,  quartz,  agate, 
sand),  and  in  the  form  of  silicates,  which  are  silicic  acid  in  which  the 
hydrogen  has  been  replaced  by  metals.  Most  of  our  common  rocks, 
such  as  granite,  porphyry,  basalt,  feldspar,  mica,  etc.,  are  such  sili- 
cates, or  a  mixture  of  them.  Small  quantities  of  silica  are  found 
in  spring  waters,  as  well  as  in  vegetable  and  animal  bodies. 

7 


98  NON-METALS  AND  THEIR  COMBINATIONS. 

Silicon  resembles  carbon  both  in  its  physical  and  chemical  proper- 
ties. Like  carbon,  it  is  known  in  the  amorphous  state,  and  forms 
two  kinds  of  crystals,  which  resemble  graphite  and  diamond.  Like 
carbon,  silicon  is  quadrivalent,  forming  silicon  dioxide,  SiO2,  silicic 
acid,  H2SiO3,  silicon  hydride,  SiH4,  silicon  chloride,  SiCl4,  which 
compounds  are  analogous  to  the  corresponding  carbon  compounds, 
C02,  H2C03,  CH4,  and  CC14. 

The  compounds  formed  by  the  union  of  silicon  with  hydrogen,  chlorine,  and 
fluorine  are  gases.  The  latter  compound,  silicon  fluoride,  SiF4,  is  obtained  by 
the  action  of  hydrofluoric  acid  on  silica  or  silicates,  thus : 

SiO2  +  4HF  =  SiF,  +  2H20. 

This  reaction  is  used  in  the  analysis  of  silicates,  which  are  decomposed  and 
rendered  soluble  by  the  action  of  hydrofluoric  acid. 

Silicon  fluoride  is  decomposed  by  water  into  silicic  acid  and  hydrofluosilicic 
acid,  H2SiF6,  thus : 

3SiF4  +  3H2O  =  H2SiO3  +  2H2SiF6. 

Several  varieties  of  silicic  acid  are  known,  of  which  may  be  mentioned  the 
normal  silicic  acid,  H4Si04,  and  the  ordinary  silicic  acid,  H2Si03,  from  the  latter 
of  which,  by  heating,  water  may  be  expelled,  when  silicon  dioxide,  SiO2,  is  left. 

Tests  for  silicic  acid  and  silicates. 

(Soluble  glass  or  flint  may  be  used  ) 

1.  Silicic  acid  and  most  silicates  are  insoluble  in  water  and  acids. 
By  fusing  silicates  with  about  5  parts  of  a  mixture  of  the  carbonates 
of  sodium  and  potassium,  the  silicates  of  these  metals  (known  as  solu- 
ble glass)  are  formed.     By  dissolving  this  salt  in  water  and  acidifying 
the  solution  with  hydrochloric  acid  a  portion  of  the  silica  separates 
as  the  gelatinous  hydroxide.     Complete  separation  of  the  silica  is 
accomplished  by  evaporating  the  mixture  to  complete  dryness  over 
a  water-bath,  and  re-dissolving  the  chlorides  of  the  metals  in  water 
acidulated  with  hydrochloric  acid;   silica  remains  undissolved  as  a 
white,  amorphous  powder. 

2.  Silica  or  silicates  when  added  to  a  bead  of  microcosmic  salt  (see 
index)   form  on  heating  before  the  blowpipe  the  so-called  silica- 
skeleton. 

Boron,  B/r/  =  1O.9,  is  found  in  but  few  localities,  either  as  boric 
(boracic)  acid  or  sodium  borate  (borax).  Formerly  the  total  supply 
of  boron  was  derived  from  Italy ;  large  quantities  of  borax  are  now 
obtained  from  Nevada. 

Boric  acid,  Acidum  boricum,  H3BO3=61.9  (Boracic  acid),  is  a 


CARBON.  99 

white,  crystalline  substance,  which  is  sparingly  soluble  in  cold  water, 
somewhat  more  soluble  in  alcohol  and  in  glycerin  ;  it  has  but  weak 
acid  properties.  When  heated  to  100°  C.  (212°  F.)  it  loses  water, 
and  is  converte'd  into  metaboric  acid,  HBO2,  which  when  heated  yet 
higher  is  converted  into  tetraborio  add,  H2B4O7,  from  which  borax, 
Na2B4O7  -f  10H2O,  is  derived.  At  a  white  heat  boric  acid  loses  all 
water,  and  is  converted  into  boron  trioxide,  B2O3 

Boric  acid  is  obtained  by  adding  hydrochloric  acid  to  a  hot  satur- 
ated solution  of  borax,  when  boric  acid  separates  on  cooling.  The 
chemical  change  is  this  : 

Na2B4O7  +  2HC1  +  5H2O  =  4H3BO3  +  2NaCl. 

Tests  for  boric  acid  and  borates. 
(Sodium  borate,  Na,B4O7.10H2O,  may  be  used. 

1.  Heat  some  borax  on  the  loop  of  a  platinum  wire.     Notice  that 
it  swells  up  during  the  time  that  water  is  expelled,  and  then  melts 
into  a  transparent,  colorless  bead  of  fused  borax. 

2.  To  a  concentrated  neutral  solution  of  a  borate  add  solution  of 
either  calcium,  barium,  or  silver.     In  either  case  white  precipitates 
of  borates  are  formed,  having  the  composition  CaB4O7,  BaB4O7,  or 


3.  Mix  in  a  porcelain  dish  some  borax  with  a  few  drops  of  sul- 
phuric acid,  pour  upon  the  mixture  some  alcohol  and  ignite.     The 
flame  has  a  seam  or  mantle  of  a  green  color,  which  is  best  seen  by 
repeatedly  extinguishing  and  rckjn.dlkig  vi^e  alcolioL.    A.  borax  bead 
moistened  with  sulphuric  acicf  and  heated  in  a  flame  also  colors  it  green. 

4.  To  a  warm  saturated  solution  of  ,a  borage  add,  sprne  hydrochloric 
or  sulphuric  acid.     On  cocking,  shining  scales  of  boric  acid  separate. 

5.  A  solution  of  borax,  even  when  acidulated  with  hydrochloric 
acid,  colors  turmeric-paper  brown,  after  this  has  been  dried. 

QUESTIONS.—  121.  How  is  carbon  found  in  nature?  122.  State  the  physical 
and  chemical  properties  of  carbon  in  its  three  allotropic  modifications.  123. 
Mention  three  different  processes  by  which  carbon  dioxide  is  generated  in 
nature,  and  some  processes  by  which  it  is  generated  by  artificial  means.  124. 
State  the  physical  and  chemical  properties  of  carbon  dioxide.  125.  Explain 
the  process  of  respiration  from  a  chemical  point  of  view.  126.  What  is  the 
percentage  of  carbon  dioxide  in  atmospheric  air,  and  why  does  its  amount  not 
increase?  127.  State  the  composition  of  carbonic  acid  and  of  a  carbonate. 
How  can  they  be  recognized  by  analytical  methods?  128.  Under  what  circum- 
stances will  carbon  monoxide  form,  and  how  does  it  act  when  inhaled  ?  129. 
What  is  destructive  distillation,  and  what  gases  are  generally  formed  during 
that  process?  130.  Explain  the  structure  and  luminosity  of  flames. 


100  NON-METALS  AND  THEIR  COMBINATIONS. 

14.   SULPHUR. 

Sii  =  32  (31.97). 

Occurrence  in  nature.  Sulphur  is  found  in  the  uncombined 
state  in  volcanic  districts,  the  chief  supply  being  derived  from 
Sicily.  In  combination  sulphur  is  widely  diffrsed  in  the  form  of 
sulphates  (gypsum,  CaSO4.2H2O),  and  frequently  as  sulphides  (iron 
pyrites,  FeS2,  galena,  PbS,  cinnabar,  HgS,  etc.).  Sulphur  enters  also 
into  organic  compounds,  during  the  decomposition  of  which  sulphur 
is  evolved  as  hydrogen  sulphide,  which  gas  is  also  a  constituent  of 
some  waters. 

Properties.  Sulphur  is  a  yellow,  brittle,  solid  substance,  having 
neither  tastejaor_ odor.  It  is  insoluble  in  water  and  nearly  so  in 
alcohol;  soluble  in  benzene,  benzin,  ether,  chloroform,  carbon 
disulphide,  oil  of  turpentine,  and  fat  oils.  Sulphur  is  polymorphous ; 
it  crystallizes,  from  a  solution  in  disulphide  of  carbon,  in  octahedrons 
with  a  rhombic  base ;  when,  however,  liquefied  by  heat  it  crystallizes 
in  six-sided  prisms,  and  is  obtained  as  a  brown,  amorphous  substance 
by  pouring  melted  sulphur  into  cold  water. 

Sulphur  melts  at  115°  C.  (239°  F.)  to  an  amber-colored  liquid, 
which  is  fluid  as  water ;  increasing  the  heat  gradually,  it  becomes 
brown  and  thick,  and  at  about  200°  C.  (392°  F.)  it  is  so  tenacious 
that  it  scarcely  flows ;  when  heated  still  further  the  sulphur  again 
becomes  tliiji- and  liquid,  and,  finally,  boilfr  ai  a  temperature  of  about 
440°  C.  (824°- 1\).  ' 

In  its 5  chemical  pr0,pe*rties,  aalphu;, •  i  ^semj^s  oxygen,  being  like 
this  element  bivalent;  a^d.  supporting,  ,wh.eix  ia  the  form  of  vapor, 
the  combustion  of  many  substances,  especially  of  metals.  Many 
compounds  of  oxygen  and  sulphur  show  an  analogous  composition, 
as  for  instance  H2O  and  H2S,  CO2  and  CS2,  CuO  and  CuS. 

Crude  sulphur  is  that  obtained  from  the  localities  where  it  is 
found.  It  contains  generally  from  2  to  4  per  cent,  of  earthy  im- 
purities. Melted  sulphur  poured  into  round  moulds  is  known  as  roll- 
sulphur  or  brimstone. 

Sublimed  sulphur,  Sulphur  sublimatum  (Flowers  of  sulphur). 
Obtained  by  heating  sulphur  to  the  boiling-point  in  suitable  vessels, 
and  passing  the  vapor  into  large  chambers,  where  it  deposits  in  the 
form  of  a  powder,  composed  of  small  crystals. 


SULPHUR.  101 

Washed  sulphur,  Sulphur  lotum,  is  sublimed  sulphur  washed 
with  a  very  dilute  ammonia  water,  and  then  with  pure  water ;  the 
object  of  this  treatment  being  to  free  the  sulphur  from  all  adhering 
sulphurous  and  sulphuric  acid,  as  also  from  arsenic  compounds  which 
are  sometimes  present. 

Precipitated  sulphur,  Sulphur  prsecipitatum  (Milk  of  sulphur). 
Made  by  boiling  one  part  of  calcium  hydroxide  with  two  parts  of 
sulphur  and  thirty  parts  of  water,  filtering  the  solution,  adding  to  it 
dilute  hydrochloric  acid  until  nearly  neutral,  washing  and  drying  the 
precipitated  sulphur. 

By  the  action  of  sulphur  on  calcium  hydroxide  are  formed  calcium  polysul- 
phide,  calcium  hyposulphite,  and  water : 

3(Ca20H)     +    12S    :  :    2CaS5    +     CaS2O3    +     3H2O. 
Calcium  Sulphur.        Calcium  Calcium  Water, 

hydroxide.  Polysulphide,    Hyposulphite. 

On  adding  hydrochloric  acid  to  the  solution,  both  substances  are  decomposed 
and  sulphur  is  liberated  : 

2CaS5  +  CaS203  +  6HC1  =  3CaCl2  +  3H2O  +  12S. 

Precipitated  sulphur  differs  from  sublimed  sulphur  by  being  in  a  more  finely 
divided  state,  and  by  having  a  much  paler  yellow,  almost  white  color. 

Sulphur  dioxide,  SO2  =  64  (Sulphurous  anhydride,  improperly 
also  called  sulphurous  acid). 

Two  combinations  of  sulphur  and  oxygen  are  known;  they  are 
sulphur  dioxide,  SO2,  and  sulphur  trioxide,  SO3. 

Sulphur  dioxide  is  formed  always  when  sulphur  or  substances  con- 
taining it  in  a  combustible  form  (H2S,  CS2,  etc.)  burn  in  air.  It  is 
formed  also  by  the  action  of  strong  sulphuric  acid  on  many  metals 
(Cu,  Hg,  Ag,  etc.),  or  on  charcoal : 

2H2SO4    +     Cu    :   :    CuSO4    +     2H2O    +    SO2. 
Sulphuric         Copper.          Cupric  Water.  Sulphur 

acid.  sulphate.  dioxide. 

2H2SO4  +  C  =  CO2  +  2H2O  +  2SO2. 

Sulphur  dioxide  is  a  colorless  gas,  having  a  suffocating,  disagreeable 
odor  ;  it  liquefies  at  a  temperature  of — 10°  C.  (14°  F.),  and  solidifies 
at — 60°  C.  ( — 76°  F.) ;  it  is  very  soluble  in  water,  forming  sulphur- 
ous acid ;  it  is  a  strong,  deoxidizing,  bleaching,  and  disinfecting 
agent ;  when  inhaled  in  a  pure  state  it  is  poisonous ;  when  diluted 
with  air  it  produces  coughing  and  irritation  of  the  air-passages. 


102  NON-METALS  AND  THEIR  COMBINATIONS. 

Sulphurous  acid,  Acidum  sulphurosum,  H2SO3  =  82.  One 
volume  of  cold  water  absorbs  about  40  volumes  of  sulphur  dioxide, 
equal  to  about  11  per  cent,  by  weight.  The  official  acid  must  contain 
not  less  than  6.4  per  cent,  by  weight,  equal  to  about  2250  volumes  of 
gas  dissolved  in  100  of  water.  According  to  the  U.  S.  P.  the  acid 
is  made  by  generating  sulphur  dioxide  from  charcoal  and  sulphuric 
acid  in  a  flask,  and  passing  the  gas  through  a  wash-bottle  containing 
water,  into  distilled  water  for  absorption. 

Experiment  10.  Use  an  apparatus  as  shown  in  Fig.  11.  Place  in  the  flask 
about  20  grammes  of  charcoal  in  small  pieces,  cover  it  with  sulphuric  acid, 
apply  heat,  and  pass  the  generated  gas  first  through  a  small  quantity  of  water 
contained  in  the  wash-bottle,  and  then  into  pure  water,  contained  in  the 
cylinder. 


FIG.  11. 


Apparatus  for  making  sulphurous  acid. 

The  solution,  sulphurous  acid,  may  be  used  for  the  tests  mentioned  below ; 
when  the  neutral  solution  of  a  sulphite  is  required,  make  this  by  adding  solu- 
tion of  sodium  carbonate  to  a  portion  of  the  sulphurous  acid  until  litmus-paper 
shows  neutral  reaction.  Examine  also  the  contents  of  the  wash-bottle  by 
means  of  the  tests  given  below  for  sulphuric  acid ;  most  likely  some  of  the 
latter  will  be  found.  How  much  carbon  and  how  much  H2S04  are  required  to 
make  100  grammes  of  a  6.4  per  cent,  sulphurous  acid  ? 

Thus  obtained,  sulphurous  acid  is  a  colorless  acid  liquid,  which  has 
the  odor  as  well  as  the  disinfecting  and  bleaching  properties  of  sulphur 
dioxide ;  it  is  completely  volatilized  by  heat.  Sulphurous  acid  is  a 
dibasic  acid,  the  salts  of  which  are  termed  sulphites. 


SULPHUR.  1()3 

Tests  for  sulphurous  acid  and  sulphites. 

(Sodium  sulphite,  Na2SO3,  may  be  used.) 

1.  Sulphurous  acid,  or  the  gaseous  sulphur  dioxide  liberated  from 
sulphites  by  the  addition  of  sulphuric  acid,  decolorizes  an  acidified 
solution  of  potassium  permanganate,  in  consequence  of  the  deoxida- 
tion  of  the  latter. 

2.  Similarly  to  the  above,  an  acid  solution  of  potassium  dichromate 
is  turned  green  by  conversion  of  chromic  acid  into  chromic  oxide. 

3.  When  sulphurous  acid  or  sulphites  are  added  to  diluted  sul- 
phuric acid  and  zinc  (which  evolve  hydrogen),  hydrogen  sulphide  is 

liberated. 

H2SO3    +    6H    ==    H2S    +    3H2O. 

4.  Barium  chloride  added  to  a  neutral  solution  of  a  sulphite  pro- 
duces a  white  precipitate  of  barium  sulphite,  soluble  in  diluted  hydro- 
chloric acid ;  barium  sulphate  is  insoluble  in  hydrochloric  acid. 

Na.2SO4     +     BaCl2    =    BaSO3     +     2NaCl. 
Sodium  Barium  Barium  Sodium 

sulphite.  chloride.          sulphite.  chloride. 

5.  Silver  nitrate  produces  a  white  precipitate  of  silver  sulphite, 
which  darkens  when  heated,  metallic  silver  and  sulphuric  acid  being 

formed : 

Ag2S03    +    H20    =    2Ag    +    H2S04. 

6.  A  strip  of  paper,  moistened  with  mercurous  nitrate  solution, 
turns  black  when  suspended  in  sulphur  dioxide. 

Sulphur  trioxide,  SO3  =  8O  (Anhydrous  sulphuric  add).  This 
is  a  white,  silk-like  solid  substance,  having  a  powerful  affinity  for 
water;  it  may  be  obtained  by  the  action  of  phosphoric  oxide  on 
strong  sulphuric  acid,  or  by  passing  sulphur  dioxide  and  oxygen 
together  over  heated  platinum-sponge ;  it  is  of  scientific  interest  only. 

Sulphuric  acid,  Acidum  sulphuricum,  H2SO4  =  98  (Oil  of 
vitriol,  Hydrogen  sulphate).  There  is  no  other  acid,  and  perhaps  no 
other  substance,  manufactured  by  chemical  action  which  is  so  largely 
used  in  chemical  operations,  and  in  the  manufacture  of  so  many  of 
the  most  important  articles,  as  is  sulphuric  acid. 

Sulphuric  acid  was  accidentally  discovered  in  the  fifteenth  century, 
and  was  then  obtained  by  heating  ferrous  sulphate  (green  vitriol)  in 
a  retort.  To  the  liquid  distilling  over,  the  name  of  oil  of  vitriol  was 
given,  in  allusion  to  the  thick  or  oily  appearance,  and  the  green 
vitriol  from  which  it  was  obtained. 


104  NON-METALS  AND  THEIR  COMBINATIONS. 

Sulphuric  acid  is  found  in  nature  in  combination  with  metals  as 
sulphates.  Thus  calcium  sulphate  (gypsum),  barium  sulphate  (heavy- 
spar),  magnesium  sulphate  (Epsom  salt),  and  others  occur  in  nature. 

Manufacture  of  sulphuric  acid.  Sulphuric  acid  is  manufactured 
on  a  very  large  scale  by  passing  into  large  leaden  chambers  simul- 
taneously, the  vapors  of  sulphur  dioxide  (obtained  by  burning  sulphur 
or  pyrites  in  furnaces),  nitric  acid,  and  steam,  a  supply  of  atmospheric 
air  also  being  provided  for.  The  most  simple  explanation  that  can 
be  given  for  the  manufacture  of  sulphuric  acid  is  the  fact  that  sul- 
phur dioxide  when  treated  with  an  oxidizing  agent,  in  the  presence 
of  water,  is  converted  into  sulphuric  acid : 

SO2    +    O    +    H2O    —    H2SO4. 

Only  a  portion  of  the  oxygen  necessary  for  oxidation  is  derived 
from  the  nitric  acid  directly ;  the  larger  quantity  is  obtained  from 
the  atmospheric  air,  the  oxides  of  nitrogen  serving  as  agents  for  the 
transfer  of  the  atmospheric  oxygen. 

By  the  action  of  nitric  acid  on  sulphur  dioxide  and  steam  are  formed  sul- 
phuric acid  and  nitrogen  trioxide : 

2SO2  +  H2O  +  2HNO3  =  2H2S04  -f  N2O3. 

Nitrogen  trioxide  next  takes  up  sulphur  dioxide,  water,  and  oxygen,  forming 
a  compound  called  nitrosyl-sulphuric  acid : 

2SO2  +  N2O3  +  2O  +  H2O*=  2(SO2.OH.N02). 

This  complex  compound  is  readily  decomposed  by  steam  into  sulphuric  acid 
and  nitrogen  trioxide : 

2(SO2.OH.N02)  +  H2O  =  2H2SO4  +  N2O3 

The  nitrogen  trioxide  again  forms  nitrosyl-sulphuric  acid,  which  again  suffers 
decomposition,  and  so  on  indefinitely,  as  long  as  the  constituents  necessary  for 
the  changes  are  supplied.  These  facts  show  that  a  given  quantity  of  nitric  acid 
will  convert  an  unlimited  amount  of  sulphurous  acid  into  sulphuric  acid. 
There  is,  however,  an  unavoidable  loss  of  small  portions  of  nitric  acid,  or 
oxides  of  nitrogen,  for  which  reason  some  nitric  acid  has  to  be  supplied  daily. 

It  is  likely  that  other  chemical  changes  than  the  ones  mentioned  take  place 
in  the  acid  chamber,  but  according  to  modern  investigations  these  are  the 
principal  ones. 

The  liquid  sulphuric  acid  formed  in  the  lead-chamber  collects  at 
the  bottom  of  the  chamber,  whence  it  is  drawn  off.  In  this  state  it 
is  known  as  chamber  acid  (specific  gravity  1.50),  and  is  not  pure,  but 
contains  about  36  per  cent,  of  water,  and  frequently  either  sulphurous 
or  nitric  acid.  By  evaporation  in  shallow  leaden  pans  it  is  further 
concentrated,  until  it  shows  a  specific  gravity  of  1.72.  When  this 


SULPHUR.  105 

point  is  reached  the  acid  acts  upon  the  lead,  wherefore  the  further 
concentration  is  conducted  in  vessels  of  glass  or  platinum,  until  a 
specific  gravity  of  1.84  is  obtained.  This  acid  contains  about  95 
per  cent,  of  sulphuric  acid ;  the  remaining  5  per  cent,  of  water  can- 
not be  expelled  by  heat. 

Properties  of  sulphuric  acid.  Pure  acid  has  a  specific  gravity  of 
1.848  ;  it  is  a  colorless  liquid,  of  oily  consistence,  boiling  at  338°  C- 
(640°  F.).  It  has  a  great  tendency  to  combine  with  water,  absorbing 
it  readily  from  atmospheric  air.  I  Upon  mixing  sulphuric  acid  and 
water,  heat  is  generated  in  consequence  of  the  combination  taking 
place  between  the  two  substances.)  To  the  same  tendency  of  sulphuric 
acid  to  combine  with  water  must  be  ascribed  its  property  of  destroy- 
ing and  blackening  organic  matter.  Organic  substances  generally 
contain  the  elements  carbon,  hydrogen,  and  oxygen.  Sulphuric  acid 
added  to  such  organic  substances  removes  the  elements  hydrogen  and 
oxygen  (or  at  least  a  portion  of  them),  combines  them  into  water, 
with  which  it  unites,  leaving  behind  compounds  so  rich  in  carbon 
that  the  black  color  predominates.  It  is  due  to  this  decomposing 
action  of  sulphuric  acid  upon  organic  matter  that  traces  of  the  latter 
color  sulphuric  acid  dark  yellow,  brown,  and,  when  present  in  larger 
quantities,  almost  black.  The  poisonous  caustic  properties  are  due 
to  the  same  action. 

Sulphuric  acid  is  a  very  strong  dibasic  acid,  which  expels  or  dis- 
places most  other  acids  ;  its  salts  are  known  as  sulphates. 

The  sulphuric  acid  of  the  U.  S.  P.  should  contain  not  less  than 
92.5  per  cent,  of  H2SO4,  corresponding  to  a  specific  gravity  of  not 
less  than  1.835. 

The  diluted  sulphuric  add,  Acidum  sulphuricum  dilutum,  is  a  mix- 
ture of  100  parts  by  weight  of  acid  and  825  parts  of  water,  or  of 
about  60  c.c.  of  acid  and  900  c.c.  of  water. 

Tests  for  sulphuric  acid  and  sulphates. 

(Sodium  sulphate,  Na2SO4,  may  be  used.) 

1.  Barium  chloride  produces  a  white  precipitate  of  barium  sulphate, 
insoluble  in  all  acids  : 

Na^    -f    BaCl3    =    BaSO4    +    2NaCl. 

2.  Soluble  lead  salts  (lead  acetate)  produce  a  white  precipitate  of 
lead   sulphate,  slightly  soluble   in   hot  concentrated  acids  and   in 
ammonium  acetate. 


106  NON-METALS  AND  THEIR  COMBINATIONS. 

3.  Sulphates,  sulphur,  or  any  compound  containing  it,  fused  on 
charcoal  with  sodium  carbonate  and  potassium  cyanide  by  means  of 
a  blowpipe,  form  hepar  (chiefly  sulphide  of  an  alkali  metal),  which, 
when  placed  upon  a  silver  coin  and  moistened  with  dilute  hydro- 
chloric acid,  causes  a  black  stain,  due  to  the  formation  of  silver  sul- 
phide. This  test  is  of  value  in  the  case  of  insoluble  sulphates,  such 
as  barium  sulphate  and  others. 

Antidotes.  Magnesia,  sodium  carbonate,  chalk,  and  soap,  to  neutralize  the 
acid. 

Sulpho-acids.  Whilst  but  two  oxides  of  sulphur  exist  in  the 
separate  state,  there  are  a  large  number  of  sulpho-acids  known. 
They  are  : 

Hydrosulphuric  acid,  H2S. 
Hyposulphurous  acid,  H2SO2. 
Sulphurous  acid,          H2SO3. 
Sulphuric  acid,  H2SO4. 

Pyrosulphuric  acid,  H2S2O7. 
Thiosulphuric  acid,  H2S2O3. 
Dithionic  acid,  H2S2O6. 

Trithionic  acid,  H2S3O6 

Tetrathionic  acid,  H2S4O6. 
Pentathionic  acid,  H2S5O6- 

Pyrosulphuric  acid,  H2S2O7  (Disulphuric  acid,  fuming  sulphuric 
acid,  Nordhausen  oil  of  vitrol).  This  acid  is  made  by  passing  sulphur 
trioxide  (obtained  by  heating  ferrous  sulphate)  into  sulphuric  acid, 
when  direct  combination  takes  place  : 

H2S04    +    S03    =    H2S207. 

It  is  a  thick,  highly  corrosive  liquid,  which  gives  off  dense  fumes 
when  exposed  to  the  air,  and  decomposes  readily  into  sulphur  trioxide 
and  sulphuric  acid  when  heated. 

Thiosulphuric  acid,  formerly  Hyposulphurous  acid,  H2S2O3,  is 
of  interest,  because  some  of  its  salts  are  used,  as,  for  instance,  sodium 
thiosulphate,  Na2S2O3,  the  sodium  hyposulphite  of  the  U.  S.  P.  The 
acid  itself  is  not  known  in  the  separate  state,  since  it  decomposes  into 
sulphur  and  sulphurous  acid  when  attempts  are  made  to  liberate  it 
from  its  salts. 

Tests  for  thiosulphates. 
(A  solution  of  sodium  thiosulphate,  Na2S2O3>  may  be  used  ) 

1.  Thiosulphates  liberate  with  sulphuric  or  hydrochloric  acid  sul- 
phur dioxide,  while  sulphur  is  set  free : 

Na2S2O3  +  H2S04  =  Na2S04  +  H2O  -f  SO2  -f  S. 


SULPHUR.  107 

2.  Silver  nitrate  and  barium  chloride  produce  white  precipitates  of 
silver  thiosulphate  and  barium  thiosulphate.  The  silver  salt  becomes 
dark  on  heating ;  the  barium  salt  is  soluble  in  much  water  and  is 
decomposed  by  hydrochloric  acid. 

Hydrogen  sulphide,  H2S  =  34.  (Hydrosulphuric  acid,  Sulphu- 
retted hydrogen.)  This  compound  has  been  mentioned  as  being  liber- 
ated by  the  decomposition  of  organic  matter  (putrefaction)  and  as  a 
constituent  of  some  spring  waters.  It  is  formed  also  during  the 
destructive  distillation  of  organic  matter  containing  sulphur.  The 
best  mode  of  obtaining  it  is  the  decomposition  of  metallic  sulphides  by 
diluted  sulphuric  or  hydrochloric  acid.  Ferrous  sulphide  is  usually 
selected  for  decomposition : 

FeS    +    H2SO4    =    FeSO4    +    H2S. 

Experiment  11.  Use  apparatus  shown  in  Fig.  11,  page  102.  Place  about  20 
grammes  of  ferrous  sulphide  in  the  flask,  cover  the  pieces  with  water,  and  add 
sulphuric  or  hydrochloric  acid.  Pass  a  portion  of  the  washed  gas  into  water, 
another  portion  into  ammonia  water.  Use  the  solutions  for  the  tests  mentioned 
below.  Ignite  the  gas  at  the  delivery  tube  and  notice  that  sulphur  is  deposited 
upon  the  surface  of  a  cold  plate  held  in  the  flame.  Place  the  apparatus  in  the 
fume  chamber  during  the  operation.  How  much  ferrous  sulphide  is  required 
to  liberate  a  quantity  of  hydrosulphuric  acid  sufficient  to  convert  1000  grammes 
of  10  per  cent,  ammonia  water  into  ammonium  sulphide  solution  ?  The  reac- 
tion taking  place  is  this : 

2NH3    +    H2S    =   :    (NH4)2S. 

Hydrogen  sulphide  is  a  colorless  gas,  having  an  exceedingly  offen- 
sive odor  and  a  disgusting  taste.  Water  absorbs  about  three  volumes 
of  the  gas,  and  this  solution  is  feebly  acid.  It  is  highly  combustible 
in  air,  burning  with  a  blue  flame,  and  forming  sulphur  dioxide  and 
water.  It  is  directly  poisonous  when  inhaled,  its  action  depending 
chiefly  on  its  power  of  reducing,  and  combining  with,  the  blood- 
coloring  matter.  Plenty  of  fresh  air,  or  air  containing  a  very  little 
chlorine,  should  be  used  as  an  antidote. 

Hydrogen  sulphide  gas  and  its  solution  in  water  are  frequently 
used  as  reagents  in  analytical  chemistry  for  precipitating  and  recog- 
nizing metals.  This  use  depends  on  the  property  of  the  sulphur  to 
combine  with  many  metals  to  form  insoluble  compounds,  the  color 
of  which  frequently  is  very  characteristic  : 

CuS04    +    H2S    :  :    CuS    +    H2SO4. 
The  salts  of  hydrosulphuric  acid  are  known  as  sulphides. 


108  NON-METALS  AND  THEIR  COMBINATIONS. 


Tests  for  hydrogen  sulphide  or  sulphides. 

1.  Hydrogen  sulphide  or  soluble  sulphides  (ammonium  sulphide 
may  be  used),  when  added  to  soluble  salts  of  lead,  copper,  mercury, 
etc.,  give  black  precipitates  of  the  sulphides  of  those  metals. 

2.  From  insoluble  sulphides  (ferrous  sulphide,  FeS,  may  be  used) 
liberate  the  gas  by  sulphuric  or  hydrochloric  acid,  and  test  as  above, 
or  suspend  a  piece  of  filter-paper,  moistened  with  solution  of  lead 
acetate,  in  the  liberated  gas,  when  the  paper  turns  dark.     Some  sul- 
phides, for  instance  those  of  mercury,  gold,  platinum,  as  also  FeS2, 
and  a  few  others,  are  not  decomposed  by  the  acids  mentioned,  unless 
zinc  be  added. 

Carbon  disulphide,  Carbonii  bisulphidum,  CS2  =  76.  This 
compound  is  obtained  by  passing  vapors  of  sulphur  over  heated 
charcoal.  It  is  a  colorless,  highly  refractive,  very  volatile,  and 
inflammable  neutral  liquid,  having  a  characteristic  odor  and  a  sharp, 
aromatic  taste.  It  boils  at  46°  C.  (115°  F.) ;  it  is  almost  insoluble 
in  water,  soluble  in  alcohol,  ether,  chloroform,  fixed  and  volatile  oils ; 
for  the  latter  two  it  is  an  excellent  solvent,  but  dissolves,  also,  many 
other  substances,  such  as  sulphur,  phosphorus,  iodine,  many  alka- 
loids, etc. 

Selenium,  Se,  and  Tellurium,  Te,  are  but  rarely  met  with.  Both  elements 
show  much  resemblance  to  sulphur ;  both  are  polymorphous ;  both  combine 
with  hydrogen,  forming  H2Se  and  H2Te,  gaseous  compounds  having  an  odor 
more  disagreeable  even  than  that  of  H2S.  Like  sulphur,  they  form  dioxides, 
Se02  and  TeO2,  which  combine  with  water,  forming  the  acids  H2SeO3  and 
H2Te03,  analogous  to  H2S03.  The  acids  H2Se04  and  H2Te04,  corresponding 
to  H2S04,  also  are  known. 

QUESTIONS. — 131.  How  is  sulphur  found  in  nature?  132.  Mention  of  sul- 
phur: atomic  weight,  valence,  color,  odor,  taste,  solubility,  behavior  when 
heated,  and  allotropic  modifications.  133.  State  the  processes  for  obtaining 
sublimed,  washed,  and  precipitated  sulphur.  134.  State  composition  and  mode 
of  preparing  sulphur  dioxide  and  sulphurous  acid;  what  are  they  used  for, 
and  what  are  their  properties  ?  135.  Explain  the  process  for  the  manufacture 
of  sulphuric  acid  on  a  large  scale.  136.  Mention  of  sulphuric  acid :  color, 
specific  gravity,  its  action  on  water  and  organic  substances.  137.  Give  tests 
for  sulphates  and  sulphites,  sulphuric  and  sulphurous  acids.  138.  What  is  the 
difference  between  sulphates,  sulphites,  and  sulphides?  139.  How  is  hydro- 
sulphuric  acid  formed  in  nature,  and  by  what  process  is  it  obtained  artificially? 
What  are  its  properties,  and  what  is  it  used  for?  140.  Mention  antidotes  in 
case  of  poisoning  by  sulphuric  and  hydrosulphuric  acids. 


PHOSPHORUS.  109 

15.  PHOSPHOEUS. 
Piii  =  31  (30  96). 

Occurrence  in  nature.  Phosphorus  is  found  in  nature  chiefly  in 
the  form  of  phosphates  of  calcium  (apatite,  phosphorite),  iron,  and 
aluminum,  which  minerals  form  deposits  in  some  localities,  but  occur 
also  diffused  in  small  quantities  through  all  soils  upon  which  plants 
will  grow,  phosphorus  being  an  essential  constituent  of  the  food  of 
most  plants.  Through  the  plants  it  enters  the  animal  system,  where 
it  is  found  either  in  organic  compounds,  or — and  this  in  by  far  the 
greater  quantity — as  tricalcium  phosphate  principally  in  the  bones, 
which  contain  about  60  per  cent,  of  it.  From  the  animal  system  it 
is  eliminated  chiefly  in  the  urine. 

Manufacture  of  phosphorus.  Phosphorus  was  discovered  and 
made  first  in  1669  by  Brandt,  of  Hamburg,  Germany,  who  obtained 
it  in  small  quantities  by  distilling  urine  previously  evaporated  and 
mixed  with  sand. 

The  manufacture  of  phosphorus  to-day  depends  on  the  deoxida- 
tion  of  metaphosphoric  acid  by  carbon  at  a  high  temperature  in 
retorts. 

The  acid  is  obtained  by  adding  to  any  suitable  tricalcium  phophate  sulphuric 
acid  in  a  quantity  sufficient  to  combine  with  the  total  amount  of  calcium 
present.  The  first  action  of  sulphuric  acid  upon  the  phosphate  consists  in  a 
removal  of  only  two-thirds  of  the  calcium  present,  and  the  formation  of  an 
acid  phosphate : 

Ca3(PO4)2  +  3H2SO4  =  CaH4(PO4)2  +  2CaSO4  +  H2SO4. 

The  nearly  insoluble  calcium  sulphate  is  separated  by  filtration,  and  the 
solution  of  acid  phosphate  containing  free  sulphuric  acid  is  evaporated  to  the 
consistency  of  a  syrup,  when  more  calcium  sulphate  separates  and  a  solution 
of  nearly  pure  phosphoric  acid  is  left  : 

CaH4(PO4)2  +  H^O,  ==  CaS04  +  2(H3PO4). 

This  syrupy  phosphoric  acid  is  mixed  with  coal  and  heated  to  a  temperature 
sufficiently  high  to  expel  water  and  convert  the  ortho-  into  meta-phosphoric 
acid: 

2(H3PO4)  =  2HP03  +  2H2O. 

The  dry  solid  mixture  of  this  acid  and  charcoal  is  now  introduced  into 
retorts  and  heated  to  a  strong  red  heat,  when  the  following  decomposition 
takes  place : 

2(HPO3)  +  5C  =  H2O  +  5CO  +  2P. 

The  three  products  formed  escape  in  the  form  of  gases  from  the  retort,  and  by 
passing  them  through  cold  water  phosphorus  is  converted  into  a  solid.  The 
reaction  in  the  retorts  is  somewhat  more  complicated  than  above  stated  in  the 


HO  NON-METALS  AND  THEIR  COMBINATIONS. 

equation,  as  some  gaseous  hydrogen  phosphide  and  a  few  other  products  are 
formed  in  small  quantities. 

Properties  of  phosphorus.  When  recently  prepared,  phos- 
phorus is  a  colorless,  translucent,  solid  substance,  which  has  some- 
what the  appearance  and  con sistency^of  "bleached  wax  In  the 
course  of  time,  and  especially  on  exposure  to  light,  it  becomes  by 
degrees  less  translucent,  opaque,  white,  yellow,  and  finally  yellowish- 
red.  At  the  freezing-point  phosphorus  is  brittle  ;  as  the  temperature 
increases  it  gradually  becomes  softer,  until  it  fuses  at  44°  C.  (111°F.), 
forming  a  yellowish  fluid,  which  at  290°  C.  (554°  F.)  (in  the  absence 
of  oxygen)  is  converted  into  a  colorless  vapor.  Specific  gravity  1.83 
at  10°  C.  (50°  F.) 

The  most  characteristic  features  of  phosphorus  are  its  great  affinity 
for  oxygen,  and  its  luminosity,  visible  in  the  dark,  from  which 
latter  property  its  name,  signifying  "bearer  of  light,"  has  been 
derived.  In  consequence  of  its  affinity  for  oxygen,  phosphorus  has 
to  be  kept  under  water,  as  it  invariably  takes  fire  when  exposed  to 
the  air,  the  slow  oxidation  taking  place  upon  the  surface  of  the 
phosphorus  soon  raising  it  to  50°  C.  (122°  F.)  at  which  temperature 
it  ignites,  burning  with  a  bright  white  flame,  and  giving  off  dense, 
white  fumes  of  phosphoric  oxide.  The  luminosity  of  phosphorus, 
due  to  this  slow  oxidation,  is  seen  when  a  piece  of  it  is  exposed  to 
the  air,  and  whitish  vapors  are  emitted  which  are  luminous  in  the 
dark  ;  at  the  same  time  an  odor  resembling  that  of  garlic  is  noticed. 

Phosphorus  is  insoluble  in  water,  sparingly  soluble  in  alcohol, 
ether,  fatty  and  essential  oils,  very  soluble  in  chloroform  and  in 
disulphide  of  carbon,  from  which  solution  it  separates  in  the  form  of 
crystals. 

Phosphorus  not  only  combines  directly  with  oxygen,  but  also  with 
chlorine,  bromine,  iodine,  sulphur,  and  with  many  metals,  the  latter 
compounds  being  known  as  phosphides. 

Phosphorus  is  trivalent  in  some  compounds,  as  in  PC13,  P2O3 ; 
quinquivalent  in  others,  as  in  PC15,  P2O6. 

The  molecules  of  most  elements  contain  two  atoms ;  phosphorus  is 
an  exception  to  this  rule,  its  molecule  containing  four  atoms.  The 
molecular  weight  of  phosphorus  is  consequently  4  X  31  =  124. 

Allotropic  modifications.  Several  allotropic  modifications  of 
phosphorus  are  known,  of  which  the  red  phosphorus  (frequently 
called  amorphous  phosphorus]  is  the  most  important.  This  variety  is 
obtained  by  exposing  common  phosphorus  for  about  two  days  to  a 


PHOSPHORUS.  Ill 

temperature  of  260°  C.  (500°  F.),  in  an  atmosphere  of  carbon  dioxide. 
Phosphorus  is  thereby  gradually  converted  into  a  red  powder,  which 
differs  widely  from  common  phosphorus.  It  is  not  poisonous,  not 
luminous,  not  soluble  in  the  solvents  above  mentioned,  not  com- 
bustible until  it  has  been  heated  to  about  280°  C.  (536°  F.),  when  it 
is  reconverted  into  common  phosphorus,  which  latter  inflames  at 
50°  C.  (122°  F.). 

Use  of  phosphorus.  By  far  the  largest  quantity  of  all  phos- 
phorus (both  common  and  red)  is  used  for  matches,  which  are  made 
by  dipping  wooden  splints  into  some  combustible  substance,  as 
melted  sulphur  or  paraffin,  and  then  into  a  paste  made  by  thoroughly 
mixing  phosphorus  with  glue  in  which  some  oxidizing  agent  (potas- 
sium nitrate  or  chlorate)  has  been  dissolved. 

Pharmaceutical  preparations  containing  phosphorus  in  the  ele- 
mentary state  are  phosphorated  oil,  pills  of  phosphorus,  and  spirit  oj 
phosphorus. 

Phosphorus  is  used  also  for  making  phosphoric  acid  and  other 
compounds. 

Poisonous  properties  of  phosphorus ;  antidotes.  Common  phosphorus  is 
extremely  poisonous,  two  kinds  of  phosphorus-poisoning  being  distinguished. 
They  are  the  acute  form,  consequent  upon  the  ingestion  of  a  poisonous  dose, 
and  the  chronic  form  affecting  the  workmen  employed  in  the  manufacture  of 
phosphorus  or  of  lucifer  matches. 

In  cases  of  poisoning  by  phosphorus,  efforts  should  be  made  to  eliminate  the 
poison  as  rapidly  as  possible  by  means  of  stomach-pump,  emetics,  or  cathartics. 
As  antidote  a  one-tenth  per  cent,  solution  of  potassium  permanganate  has  been 
used  successfully;  it  acts  by  oxidizing  the  phosphorus,  converting  it  into 
ortho-phosphoric  acid.  Oil  of  turpentine  has  also  been  used  as  an  antidote, 
though  its  action  has  not  been  sufficiently  explained.  Oil  or  fatty  matter 
(milk)  must  not  be  given,  as  they  act  as  solvents  of  the  phosphorus,  causing  its 
more  ready  assimilation. 

Detection  of  phosphorus  in  cases  of  poisoning.  Use  is  made  of  its  luminous 
properties  in  detecting  phosphorus,  when  in  the  elementary  state.  Organic 
matter  (contents  of  stomach,  food,  etc.)  containing  phosphorus  will  often  show 
this  luminosity  when  agitated  in  the  dark.  If  this  process  fails,  in  consequence 
of  too  small  a  quantity  of  the  poison,  a  portion  of  the  matter  to  be  examined 
is  rendered  fluid  by  the  addition  of  water,  slightly  acidulated  with  sulphuric 
acid,  and  placed  in  a  flask,  which  is  connected  with  a  bent  glass  tube  leading 
to  a  Liebig's  condenser.  The  apparatus  (Fig.  12)  is  placed  in  the  dark,  and 
the  flask  is  heated.  If  phosphorus  be  present,  a  luminous  ring  will  be  seen 
where  the  glass  tube,  leading  from  the  flask,  enters  the  condenser.  The  heat 
should  be  raised  gradually  to  the  boiling-point,  the  liquid  kept  boiling  for 
some  time,  and  the  products  of  distillation  collected  in  a  glass  vessel.  Phos- 


112  NON-METALS  AND  THEIR  COMBINATIONS. 

phorus  volatilizes  with  the  steam,  and  small  globules  of  it  may  be  found  in  the 
collected  fluid.  If,  however,  the  quantity  of  phosphorus  in  the  examined 
matter  was  very  small,  it  may  all  have  become  oxidized  during  the  distillation, 
and  the  fluid  will  then  contain  phosphorous  acid,  the  tests  for  which  will  be 
stated  below. 

FIG.  12. 


Apparatus  for  detection  of  phosphorus  in  cases  of  poisoning. 

It  should  be  mentioned  that  the  luminosity  of  phosphorus  vapors  is  dimin- 
ished, or  even  prevented,  by  vapors  of  essential  oils  (oil  of  turpentine,  for 
instance),  ether,  olefiant  gas,  and  a  few  other  substances. 

Oxides  of  phosphorus.  Two  oxides  of  phosphorus  are  known 
in  the  separate  state.  They  are  phosphorus  trioxide  or  phosphorous 
oxide,  P2O3,  and  phosphorus pentoxide  or  phosphoric  oxide,  P2O5.  The 
first  is  obtained  by  slow  oxidation  of  phosphorus,  the  second  by 
burning  phosphorus  in  dry  air  or  oxygen.  Both  oxides  are  white 
solids,  which  combine  readily  with  water,  forming  the  four  acids 
mentioned  below. 

No  oxides  corresponding  to  hypophosphorous  acid,  H3PO2,  and 
hypophosphoric  acid,  H2PO3,  are  known. 


PHOSPHORUS.  113 

Phosphorous  acid,  H3PO3  =  82.  This  acid  is  obtained  by  dis- 
solving phosphorous  oxide  in  water  : 

P203    +    3H20    =    2H3P03. 

It  is  a  colorless,  acid  liquid,  which  forms  salts  known  as  phos- 
phites; it  is  a  strong  deoxidizing  agent,  easily  absorbing  oxygen, 
forming  phosphoric  acid. 

Tests  for  phosphorous  acid. 

1.  Added  to  mercuric  chloride,  a  white  precipitate  of  mercurous 
chloride  is  formed. 

2.  Added  to  silver  nitrate,  a  black  precipitate  of  metallic  silver  is 
produced. 

3.  After  being  heated  with  nitric  acid,  it  shows  reactions  of  phos- 
phoric acid. 

Phosphoric  acids.  Phosphoric  oxide  is  capable  of  combining 
chemically  with  one,  two,  or  three  molecules  of  water,  forming 
thereby  three  diiferent  acids. 

P2O5  +     H2O  =  H2P2O6  =  2HPO3   Metaphosphoric  acid. 
P2O5  +  2H2O  =  H4P2O7  Pyrophosphoric  acid. 

.P2O5  +  3H2O  =  H6P2O8  =  2H3PO4  Ortho-phosphoric  acid. 

These  three  acids  show  different  reactions,  act  differently  upon  the 
animal  system,  and  form  different  salts. 

Metaphosphoric  acid,  HPO3  =  80  (Glacial  phosphoric  acid). 
This  acid  is  always  formed  when  phosphoric  oxide  is  dissolved  in 
water ;  gradually,  and  more  rapidly  on  heating  with  water,  it  absorbs 
the  latter,  forming  orthophosphoric  acid  ;  by  evaporating  the  latter 
sufficiently,  metaphosphoric  acid  is  re-formed. 

Metaphosphoric  acid  is  a  monobasic  acid  which  coagulates  albumin 
(pyro-  and  orthophosphoric  acids  do  not)  and  gives  a  white  precipi- 
tate with  ammonio  silver  nitrate ;  it  is  not  precipitated  by  magnesium 
sulphate  in  the  presence  of  ammonia  and  ammonium  chloride.  It 
acts  as  a  poison,  whilst  common  phosphoric  acid  is  comparatively 
harmless. 

Pyrophosphoric  acid,  H4P2O7  =  178.  This  is  a  tetra-basic  acid 
which  gives  a  white  precipitate  with  arnmonio-silver  nitrate,  whilst 
orthophosphoric  acid  gives  a  yellowish  precipitate  ;  it  is  not  precipi- 
tated by  ammonium  molybdate,  and  does  not  coagulate  albumin. 

8 


114  NON-METALS  AND  THEIR  COMBINATIONS. 

Phosphoric  acid,  Orthophosphoric  acid,  Acidum  phosphoricum 
H3PO4=98  (Trihydric phosphate,  Common  or  tribasic phosphoric  acid). 
Nearly  all  phosphates  found  in  nature  are  orthophosphates. 

Phosphoric  acid  may  be  made  by  burning  phosphorus,  dissolving 
the  phosphoric  oxide  in  water,  and  boiling  for  a  sufficient  length  of 
time  to  convert  the  meta-  into  orthophosphoric  acid. 

Experiment  12.  Place  a  piece  of  phosphorus  (about  0.5  gramme),  after  having 
dried  it  quickly  between  filter  paper,  in  a  small  porcelain  dish,  standing  upon 
a  glass  plate ;  ignite  the  phosphorus  by  touching  it  with  a  heated  wire,  and 
place  over  the  dish  an  inverted  large  beaker.  The  white  vapors  of  phosphoric 
oxide  soon  condense  into  flakes,  which  fall  on  the  glass  plate.  Collect  the 
white  mass  with  a  glass  rod,  and  dissolve  in  a  few  c.c.  of  water.  Use  a  portion 
of  the  solution  for  tests  of  metaphosphoric  acid;  evaporate  the  remaining 
quantity  in  a  porcelain  dish  until  it  becomes  syrupy,  dilute  with  water  and  use 
it  for  making  tests  for  orthophosphoric  acid,  either  as  such  or  after  having 
neutralized  with  sodium  carbonate.  How  much  phosphorus  is  needed  to  make 
490  grammes  of  the  U.  S.  P.  50  per  cent,  phosphoric  acid  ? 

Phosphoric  acid  is  also  made  by  gently  heating  pieces  of  phos- 
phorus with  diluted  nitric  acid,  when  the  phosphorus  is  oxidized, 
red  fumes  of  nitrogen  tetroxide  escaping  : 

3P  +  5HNO3  +  2H2O  =  3H3PO4  +  5NO. 

The  liquid  is  evaporated  until  the  excess  of  nitric  acid  has  been 
expelled,  and  enough  of  water  added  to  obtain  an  acid  which  con- 
tains 85  per  cent,  of  the  pure  H3PO4.  Specific  gravity  1.710. 

Diluted  phosphoric  acid,  U.  S.  P.,  is  made  by  mixing  100  c.c.  of  the 
85  per  cent,  acid  with  750  c  c.  of  water.  It  contains  10  per  cent,  of 
absolute  orthophosphoric  acid. 

Phosphoric  acid  is  a  colorless,  odorless,  strongly  acid  liquid,  which, 
on  heating,  loses  water,  and  finally  is  volatilized  at  a  low  red  heat. 
It  is  a  tribasic  acid,  forming  three  series  of  salts,  namely  : 

Na3PO4  =  Trisodium  phosphate. 

Na2HPO4         =  Disodium  hydrogen  phosphate. 
NaH2PO4        =  Sodium  dihydrogen  phosphate. 

If  the  metal  be  bivalent,  the  formulas  are  thus  : 

Ca3(PO4)2        =  Tricalcium  phosphate. 
Ca.,H2(PO4)2    =  Dicalcium  orthophosphate. 
CaH4(PO4)2     =  Monocalcium  orthophosphate. 

According  to  the  number  of  hydrogen  atoms  replaced  in  the  acid, 
the  salts  formed  are  also  termed  primary,  secondary,  and  tertiary 
phosphates ;  KH2PO4  being,  for  instance,  primary  potassium  phos- 
phate ;  Na2HPO4  secondary  sodium  phosphate ;  Ag3PO4  tertiary  sil- 
ver phosphate. 


PHOSPHORUS.  115 

Tests  for  phosphoric  acid  and  phosphates. 

(Sodium  phosphate,  Na2HPO4,  may  be  used.) 

1.  Add  to  phosphoric  acid,  or  to  an  aqueous  solution  of  a  phos- 
phate, a  mixture  of  magnesium  sulphate,  ammonium  chloride,  and 
ammonia  water ;  a  white  crystalline  precipitate  falls,  which  is  dimag- 
nesium  ammonium  phosphate : 

H3P04  +  MgS04  +  3NH4OH  =  MgNH4PO4  +  (NH4)2SO4  +  3H2O; 
Na2HP04  +  MgS04  +  NH4OH  =  MgNH4PO4  +  Na2SO4  +  H2O. 

2.  Add  to  a  neutral  solution  of  a  phosphate,  silver  nitrate  ;  a  yel- 
low precipitate  of  silver  phosphate  is  produced,  which  is  soluble  both 
in  ammonia  and  nitric  acid  : 

Na3P04  +  3AgN08  =  Ag3PO4  +  SNaNO,. 

3.  Add  to  phosphoric  acid,  or  to  a  phosphate  dissolved  in  water 
or  in  nitric  acid,  an  excess  of  a  solution  of  ammonium  molybdate  in 
dilute  nitric  acid,  and  apply  heat ;  a  yellow  precipitate  of  phospho- 
molybdate  of  ammonium,  (NH4)3PO4.10MoO3.2H2O,  is  produced ; 
the  precipitate  is  readily  soluble  in  ammonia  water.     This  test  is  by 
far  the  most  delicate,  and  even  traces  of  phosphoric  acid  may  be 
recognized  by  it ;  moreover,  it  can  be  used  in  an  acid  solution,  while 
the  first  two  tests  cannot. 

4.  Add  to  a  neutral  solution  of  a  phosphate,  calcium  or  barium 
chloride ;  a  white  precipitate  of  calcium  or  barium  phosphate  is  pro- 
duced, which  is  soluble  in  acids. 

5.  Ferric  chloride  produces  in  neutral  solution  a  yellowish- white 
precipitate  of  ferric  phosphate,  Fe2(PO4)2,  thus  : 

2Na2HPO4  +  Fe2Cl6  =  Fe2(PO4)2  +  4NaCl  +  2HC1. 

The  liberated  hydrochloric  acid  dissolves  some  of  the  precipitate, 
which  may  be  avoided  by  adding  previously  some  sodium  acetate ; 
the  hydrochloric  acid  combines  with  the  sodium  of  the  acetate,  and 
the  acetic  acid  w^hich  is  set  free  has  no  dissolving  action  upon  the 
ferric  phosphate. 

Hypophosphorous  acid,  H3PO2,  or  HPH2O2.  When  phosphorus 
is  heated  with  solution  of  potassium,  sodium,  or  calcium  hydroxide, 
the  hypophosphite  of  these  metals  is  formed,  while  gaseous  hydrogen 
phosphide,  PH3,  is  liberated  and  ignites  spontaneously.  The  action 
may  be  represented  thus  : 

3KOH  +  4P  +  3H2O  =  3KPH2O2  -f  PH3. 
or 

3Ca(OH)2  +  8P  +  6H2O  =  3Ca(PH2O2)2  +  2PH3. 


116  NON-METALS  AND  THEIR  COMBINATIONS. 

From  calcium  hype-phosphite  the  acid  may  be  obtained  by  decom- 
posing the  salt  with  oxalic  acid,  which  forms  insoluble  calcium 
oxalate,  while  hypophosphorous  acid  remains  in  solution : 

Ca(PHa02)2  +  H2C203  =  CaC203  +  2HPH2O2. 

From  potassium  hypophosphite  the  acid  may  be  liberated  by  the 
addition  of  tartaric  acid  and  alcohol,  when  potassium  acid  tartrate 
forms,  which  is  nearly  insoluble  in  dilute  alcohol  and  may  be  sepa- 
rated by  filtration. 

Pure  hypophosphorous  acid  is  a  white  crystalline  substance,  acting 
energetically  as  a  deoxidizing  agent.  Although  containing  three 
atoms  of  hydrogen,  it  is  a  monobasic  acid,  only  one  of  the  hydrogen 
atoms  being  replaceable  by  metals. 

The  diluted  hypophosphorous  acid,  Acidum  hypophosphorosum  dilu- 
tum  of  the  U.S. P.,  contains  10  per  cent,  of  absolute  acid.  It  is  a 
colorless  acid  liquid,  which,  upon  heating,  loses  water  and  is  afterward 
decomposed  into  phosphoric  acid  and  hydrogen  phosphide,  which 

ignites : 

2HPH202    =    H3P04    +    PH3. 

Tests  for  hypophosphites. 
(Sodium  hypophosphite,  NaPH2O2,  may  be  used.) 

1.  Heated  over  a  flame  they  burn  with  a  phosphorescent  light,  in 
consequence  of  their  decomposition  into  inflammable  hydrogen  phos- 
phide and  a  phosphate. 

2.  From  solutions  of  mercuric  chloride  and  silver  nitrate  they 
precipitate  the  metals  in  consequence  of  the  deoxidizing  action  of 
hypophosphorous  acid. 

3.  With  zinc  and  diluted  sulphuric  acid  they  evolve  hydrogen  and 
phosphoretted  hydrogen . 

4.  An  acid  solution  of  potassium  permanganate  is  readily  decolor- 
ized. 

5.  Ammonium  molybdate  solution  produces  a  blue  precipitate ;  a 
green  color  would  indicate  the  presence  of  a  phosphate,  which  alone 
gives  a  yellow  precipitate  with  the  reagent. 

Hydrogen  phosphide,  PH3  (Phosphoretted  hydrogen,  phosphine).  The  forma- 
tion of  this  compound  has  been  mentioned  in  the  previous  paragraph.  It  is  a 
colorless,  badly  smelling,  poisonous  gas,  which  when  generated  as  directed 
above,  is  spontaneously  inflammable.  This  last-named  property  is  due  to  the 
presence  of  small  quantities  of  another  compound  of  phosphorus  and  hydrogen 
which  has  the  composition  P2H4,  and  is  spontaneously  inflammable,  while  the 
compound  PH3  is  not. 


CHLORINE.  117 

Hydrogen  phosphide  corresponds  to  the  analogous  composition  of  ammonia, 
NH3.  While  the  latter  is  readily  soluble  in  water,  and  has  strong  basic  prop- 
erties, hydrogen  phosphide  is  but  sparingly  soluble  in  water,  and  its  basic  prop- 
erties are  very  weak.  However,  a  few  salts,  such  as  the  phosphonium  chloride, 
PH4C1,  analogous  to  ammonium  chloride,  NH4C1,  are  known. 

16.  CHLORINE. 

Cli  =  35.4  (35.37). 

Haloids  or  Halogens.  The  four  elements,  fluorine,  chlorine, 
bromine,  and  iodine,  which  form  a  natural  group  of  elements,  are 
known  as  haloids^  or  halogens.  The  relation  shown  by  the  atomic 
weights  of  tMse  four  elements  has  been  mentioned  in  connection  with 
the  consideration  of  natural  groups  of  elements  generally  (see  page 
63).  In  many  other  respects  a  resemblance  or  relation  can  be  dis- 
covered. For  instance :  All  haloids  are  ipiixalejit -.elements,  they 
combine  with  hydrogen,  forming  the  acids  HF,  HC1,  HBr,  HI ;  they 
combine  directly  with  most  metals,  forming  fluorides,  chlorides, 
bromides,  and  iodides.  The  relative  combining  energy  lessens  as  the 
atomic  weight  increases ;  fluorine  with  the  lowest  atomic  weight  hav- 
ing the  greatest,  iodine  with  the  highest  atomic  weight  the  smallest, 
affinity  for  other  elements.  The  first  two  members  of  the  group  are 
gases,  the  third  (bromine)  is  a  liquid,  the  last  (iodine)  'a  solid,  at 
ordinary  temperature.  They  all  show  a  distinct  color  in  the  gaseous 
state,  feave  a  disagreeable  odor,  and  possess  disinfecting  properties. 

Occurrence  in  nature.  Chlorine  is  found  chiefly  as  sodium 
chloride  or  common  salt,  NaCl,  either  dissolved  in  water  (small 
quantities  in  almost  every  spring  water,  larger  quantities  in  some 
mineral  waters,  and  the  principal  amount  in  sea- water),  or  as  solid 
deposits  in  the  interior  of  the  earth  as  rock  salt. 

QUESTIONS. — 141.  In  what  forms  of  combination  is  phosphorus  found  in 
nature  ?  142.  Give  an  outline  of  the  process  for  manufacturing  phosphorus. 
143.  What  are  the  symbol,  valence,  atomic  and  molecular  weights  of  phos- 
phorus ?  144.  State  the  chemical  and  physical  properties  both  of  common  and 
red  phosphorus.  145.  By  what  methods  may  phosphorus  be  detected  in  cases 
of  poisoning?  146.  What  two  oxides  of  phosphorus  are  known;  what  is  their 
composition,  and  what  four  acids  do  they  form  by  combining  with  water  ?  147. 
State  the  official  process  for  making  phosphoric  acid,  and  what  are  its  proper- 
ties? 148.  By  what  tests  may  the  three  phosphoric  acids  be  recognized  and 
distinguished  from  phosphorous  acid  ?  149.  What  is  a  phosphide,  phosphite, 
phosphate,  and  hypophosphite?  150.  What  is  glacial  phosphoric  acid,  and  in 
what  respect  does  its  action  upon  the  animal  system  differ  from  the  action  of 
common  phosphoric  acid. 


118  NON-METALS  AND  THEIR  COMBINATIONS. 

Other  chlorides,  such  as  those  of  potassium,  magnesium,  calcium, 
also  are  found  in  nature.  As  common  salt,  chlorine  enters  the  animal 
system,  taking  there  an  active  part  in  many  of  the  physiological  and 
chemical  changes. 

Preparation  of  chlorine.  Most  methods  of  liberating  chlorine 
depend  on  an  oxidation  of  the  hydrogen  of  hydrochloric  acid  by 
suitable  oxidizing  agents,  the  hydrogen  being  converted  into  water, 
whilst  chlorine  is  set  free. 

As  oxidizing  agents,  may  be  used  potassium  chlorate,  potassium 
bichromate,  potassium  permanganate,  chromic  acid,  nitric  acid,  and 
many  other  substances. 

The  most  common  and  cheapest  mode  of  obtaining  chlorine  is  to 
heat  manganese  dioxide,  usually  called  black  oxide  of  manganese, 
with  hydrochloric  acid,  or  a  mixture  of  manganese  dioxide  and 
sodium  chloride  with  sulphuric  acid  : 

Mn02  -f  4HC1  =  MnCl2  +  2H2O  -f  2C1. 

Chlorine  is  liberated  also  by  the  action  of  sulphuric  or  hydro- 
chloric acid  on  bleaching-powder,  which  is  a  mixture  of  calcium 
chloride  and  calcium  hypochlorite  : 

CaCl2.Ca(ClO)2  +  2H2SO4  =  2CaSO4  +  2H2O  +  4C1. 

Experiment  13.  Use  apparatus  as  in  Fig.  8,  page  86.  Conduct  operation  in  a 
fume-chamber.  Place  about  50  grammes  of  manganese  dioxide  in  coarse 
powder  in  the  flask,  cover  it  with  hydrochloric  acid,  shake  up  well  to  insure 
that  no  dry  powder  be  left  at  the  bottom  of  the  flask,  apply  heat,  and  collect 
the  gas  in  dry  bottles  by  downward  displacement.  Keep  the  bottles  loosely 
covered  with  pieces  of  stiff  paper  while  filling  them.  Use  the  gas  for  the 
following  experiments : 

a.  Fill  a  test-tube  with  chlorine,  a  second  test-tube  of  same  size  with  hydro- 
gen ;  place  them  over  one  another  so  that  the  gases  mix  by  diffusion,  then 
hold  them  near  a  flame ;  a  rapid  combustion  or  explosion  ensues. 

b.  Hold  in  one  of  the  bottles  filled  with  chlorine  a  lighted  wax  candle,  and 
notice  that  it  continues  to  burn  with  liberation  of  carbon.     The  hydrogen  con- 
tained in  the  wax  is  in  this  case  the  only  constituent  of  the  wax  which  burns, 
i.  e.,  combines  with  chlorine. 

c.  Moisten  a  paper  with  oil  of  turpentine,  C10H16,  and  drop  it  into  another 
bottle  filled  with  the  gas ;  combustion  ensues  spontaneously,  a  black  smoke  of 
carbon  being  liberated. 

d.  Drop  some  finely  powdered  antimony  into  another  bottle,  and  notice  that 
each  particle  of  the  metal  burns  while  passing  through  the  gas,  forming  white 
antimonous  chloride,  SbCl3. 

e.  Pass  some  chlorine  gas  into  water,  and  suspend  in  the  chlorine  water  thus 
formed  colored  flowers  or  pieces  of  dyed  cotton,  and  notice  that  the  color  fades 
and  in  many  cases  disappears  completely  in  a  few  hours. 


CHLORINE.  119 

Properties.  Chlorine  is  a  yellowish-green  gas,  having  a  disagree- 
able taste  and  an  extremely  penetrating,  suffocating  odor,  acting 
energetically  upon  the  air-passages,  producing  violent  coughing  and 
inflammation.  It  is  about  two  and  a  half  times  heavier  than  air, 
soluble  in  water,  and  convertible  into  a  greenish-yellow  liquid  by  a 
pressure  of  about  six  atmospheres. 

Chemically,  the  properties  of  chlorine  are  well  marked,  and  there 
are  but  few  elements  which  have  as  strong  an  affinity  for  other  ele- 
ments as  chlorine ;  it  unites  with  all  of  them  directly,  except  with 
oxygen,  nitrogen,  and  carbon,  but  even  with  these  it  may  be  made  to 
combine  indirectly.  The  act  of  combination  between  chlorine  and 
other  elements  is  frequently  attended  by  the  evolution  of  so  much 
heat  that  light  is  produced,  or,  in  other  words,  combustion  takes  place. 
Thus,  hydrogen,  phosphorus,  and  many  metals  burn  easily  in  chlorine. 
The  affinity  between  chlorine  and  hydrogen  is  intense,  a  mixture  of 
the  two  gases  being  highly  explosive.  Such  a  mixture,  kept  in  the 
dark,  will  not  undergo  chemical  change,  but  when  ignited,  or  when 
exposed  to  direct  sunlight,  the  combination  occurs  instantly  with  an 
explosion.  The  affinity  of  chlorine  for  hydrogen  is  also  demonstrated 
by  its  property  of  decomposing  water,  ammonia,  and  many  hydro- 
carbons (compounds  of  carbon  with  hydrogen),  such  as  oil  of  turpen- 
tine, C10H16,  and  others  : 

H2O  +    2C1  =    2HC1  -f      O. 

NH3     +    3C1  =     3HC1  +      N. 

C10HI6    +  16C1  =  16HC1  +  IOC. 

As  shown  by  these  formulas,  hydrochloric  acid  is  formed,  whilst 
the  other  elements  are  set  free. 

Chlorine  is  a  strong  disinfecting,  deodorizing,  and  bleaching  agent ; 
it  acts  as  such  either  directly  by  combining  with  certain  elements  of 
the  coloring  or  odoriferous  matter,  or,  indirectly,  by  decomposing 
water  with  liberation  of  oxygen,  which  in  the  nascent  state — that  is, 
at  the  moment  of  liberation — has  a  strong  tendency  to  oxidize  other 
substances. 


Chlorine  water,  Aqua  chlori,  is  water  saturated  with  pure  chlorine 
at  a  temperature  of  about  10°  C.  (50°  F.).  One  volume  of  water 
absorbs  at  that  temperature  about  two  volumes  of  chlorine,  which  is 
equal  to  0  4  per  cent,  by  weight.  Chlorine  water  is  a  greenish-yellow 
liquid,  having  the  odor  and  taste  of  chlorine.  It  must  be  kept  in  the 
dark,  as  otherwise  decomposition  takes  place. 


120  NON-METALS  AND  THEIR  COMBINATIONS. 

Hydrochloric  acid,  Acidum  hydrochloricum,  HCl=36.4(CAfor- 
hydric  add,  Muriatic  acid.  Hydrogen  chloride).  One  volume  of  hydro- 
gen combines  with  one  volume  of  chlorine  to  form  two  volumes  of 
hydrochloric  acid  : 

Another  method  for  obtaining  it  is  the  decomposition  of  a  chloride 
by  sulphuric  acid  : 

NaCl  +  H2SO4  =    HC1  +  NaHSO4; 
or 

H2SO4  =  2HC1  +  Na2SO4. 


Experiment  14.  Use  apparatus  as  in  Fig.  8,  page  86.  Place  about  20  grammes 
of  sodium  chloride  into  the  flask  (which  should  be  provided  with  a  funnel-tube) 
and  add  about  30  c.c.  of  concentrated  sulphuric  acid;  mix  well,  apply  heat,  and 
pass  the  gas  into  water  for  absorption.  If  a  pure  acid  be  desired,  the  gas  has 
to  be  passed  through  water  contained  in  a  wash-bottle  ;  apparatus  shown  in 
Fig.  11,  page  102,  may  then  be  used.  Use  the  acid  made  for  tests  mentioned 
below.  How  much  of  the  U.  S.  P.  31.9  per  cent,  hydrochloric  acid  can  be 
made  from  117  pounds  of  sodium  chloride  ? 

Hydrochloric  acid  is  a  colorless  gas,  has  a  sharp,  penetrating  odor, 
and  is  very  irritating  when  inhaled.  It  is  neither  combustible  nor 
a  supporter  of  combustion,  and  has  great  affinity  for  water,  which 
property  is  the  cause  of  the  formation  of  white  clouds  whenever  the  gas 
comes  in  contact  with  the  vapors  of  water,  or  with  moist  air  ;  the  white 
clouds  being  formed  of  minute  particles  of  liquid  hydrochloric  acid. 

Whilst  hydrochloric  acid  is  a  gas,  this  name  is  used  also  for  its 
solution  in  water,  one  volume  of  which  at  ordinary  temperature  takes 
up  over  400  volumes  of  the  gas. 

The  hydrochloric  acid  of  the  U.  S.  P.  is  an  acid  containing  31.9 
per  cent,  of  HC1.  It  is  a  colorless,  fuming  liquid,  having  the  odor 
of  the  gas,  strong  acid  properties,  and  a  specific  gravity  of  1.163. 
The  official  diluted  hydrochloric  acid  is  made  by  mixing  100  parts 
by  weight  of  the  above  acid  with  219  parts  of  water.  It  contains  10 
per  cent,  of  HC1. 

The  same  antidotes  may  be  used  as  for  nitric  acid. 

Tests  for  hydrochloric  acid  and  chlorides. 

(Sodium  chloride,  NaCl,  may  be  used.) 

1.  To  hydrochloric  acid,  or  to  solution  of  chlorides,  add  silver 
nitrate  :  a  white,  curdy  precipitate  is  produced,  which  is  soluble  in 
ammonia  water,  but  insoluble  in  nitric  acid  : 

AgN03     +     NaCl    =     NaN03     +     AgCl  ; 
AgN03    +      HC1     =      HN03    +     AgCl. 


CHLORINE.  121 

2.  Add  solution  of  mercurous  salt  (mercurous  nitrate) :  a  white 
precipitate  is  produced,  which  blackens  on  the  addition  of  ammonia: 

Hg22NO3     +     2NaCl    =    2NaNO3     +     Hg2Cl2. 

3.  Add  solution  of  lead  acetate :  a  white  precipitate  of  lead  chloride 
is  formed,  which  is  soluble  in  hot,  or  in  much  cold  water,  and  is,  there- 
fore, not  formed  in  dilute  solutions. 

4.  To  a  dry  chloride  add  strong  sulphuric  acid  and  heat :  hydro- 
chloric acid  gas  is  evolved,  which  may  be  recognized  by  the  odor,  or 
by  its  action  on  silver  nitrate. 

5.  Chlorides  treated  with  sulphuric  acid  and  manganese  dioxide 
evolve  chlorine. 

Nitre-hydrochloric  acid,  Aqua  reg-ia  (Nitro-muriatic  add).  Ob- 
tained by  mixing  40  c.c.  of  nitric  acid  with  180  c.c.  of  hydrochloric 
acid.  The  two  acids  act  chemically  upon  each  other,  forming 
chloronitrous  or  chloronitric  gas,  chlorine,  and  water  : 

HNO3    +    3HC1    =    NOC1      +     2H2O    -f     2C1 , 
HNO3    +    3HC1    =    NOC12    +     2H2O    +      Cl. 

The  dissolving  power  of  this  acid  upon  gold  and  platinum  depends 
on  the  action  of  the  free  chlorine  and  the  action  of  the  chloronitrous 
and  chloronitric  gases,  both  of  which  part  easily  with  their  chlorine. 

The  official  diluted  nitro-hydrochloric  add  is  made  by  mixing  the  acids  in  the 
quantities  above  mentioned  and  adding,  when  effervescence  has  ceased,  780  c.c. 
of  water. 

Compounds  of  chlorine  with  oxygen.  There  is  no  method 
known  by  which  to  combine  chlorine  and  oxygen  directly,  all  the 
compounds  formed  by  the  union  of  these  elements  being  obtained  by 
indirect  processes.  The  oxides  of  chlorine  are  the  following : 

Chlorine  monoxide  or  hypochlorous  oxide,  C12O. 
Chlorine  trioxide  or  chlorous  oxide,  C12O3. 

Chlorine  dioxide,  C1O2- 

All  these  oxides  are  yellow  or  greenish-yellow  gases ;  the  first  and 
second  combine  with  water,  forming  the  hypochlorous  and  chlorous 

acids : 

C12O     +    H2O    =    2HC1O. 
C1203    +    H20    =    2HC1O2. 

The  oxides  C12O5  and  C12O7  from  which  chloric  acid,  HC1O3,  and 
perchloric  acid,  HC1O4 ,  might  be  formed,  are  not  known.  The  chlo- 
rine oxides,  the  acids,  and  many  of  their  salts  are  distinguished  by 
the  great  facility  with  which  they  decompose,  frequently  with  violent 


122  NON-METALS  AND  THEIE  COMBINATIONS. 

explosion,  for  which  reason  care  must  be  taken  in  the  preparation 
and  handling  of  these  compounds. 

Chlorine  acids. 

Hydrochloric  acid,  HC1. 

Hypochlorous  acid,  HC1O. 

Chlorous  acid,  HC1O2. 

Chloric  acid,  HC1O3. 

Perchloric  acid,  HC1O4. 

With  the  exception  of  hydrochloric  acid,  which  has  been  considered, 
none  of  the  five  acids  is  of  practical  interest  as  such,  but  many  of 
« the  salts  of  hypochlorous  and  chloric  acids,  known  as  hypochlorites 
and  chlorates  respectively,  are  of  great  and  general  importance. 

Hypochlorous  acid,  HC1O,  may  be  obtained  by  the  action  of 
chlorine  water  on  mercuric  oxide,  insoluble  mercuric  oxychloride 
being  formed  also : 

2HgO  +  4C1  +  H2O  =  Hg2OCl  +  2HC1O. 

Hypochlorous  acid  is  a  colorless,  monobasic  acid  possessing  strong 
bleaching  properties. 

Hypochlorites  are  formed  by  the  action  of  chlorine  on  the  hydrox- 
ides of  potassium,  sodium,  calcium,  etc.,  at  the  ordinary  temperature : 

2NaOH  +  2C1  =  NaCl  +  NaCIO  +  H20. 

Chloric  acid,  HC1O3,  may  be  obtained  from  potassium  chlorate  by 
the  action  of  hydrofluosilicic  acid;  it  is,  however,  an  unstable  sub- 
stance which  will  decompose,  frequently  with  a  violent  explosion. 
Chlorates  are  generally  obtained  by  the  action  of  chlorine  on  alkali 
hydroxides  at  a  temperature  of  about  100°  C.  (212°  F.) 
6KOH  +  6C1  =  5KC1  +  KC1O3  +  3H2O. 

Mixtures  of  hypochlorites  and  chlorides  are  converted  into  chlo- 
rates by  boiling  their  solution : 

3KC1  +  3KC1O  =  5KC1  +  KC1O3. 

• 

Tests  for  chlorates  and  hypochlorites. 

(Potass-  chlorate,  KC1O3,  and  bleaching  powder,  Ca2ClO.CaCl2,  may  be  used.) 

1.  Chlorates  liberate  oxygen  when  heated  by  themselves. 

2.  Chlorates   liberate   chlorous    tetroxide,    C12O4,   a   deep-yellow 
explosive  gas,  on  the  addition  of  strong  sulphuric  acid. 


BROMINE— IODINE- FLUORINE.  123 

3.  Chlorates  deflagrate  when  sprinkled  on  red-hot  charcoal. 

4.  Hypochlorites  evolve  a  peculiarly  smelling  gas  (hypochlorous 
acid)  on  the  addition  of  acids,  and  are  strong  bleaching  agents. 


17.    BEOMINE— IODINE  -FLUORINE. 

Bromine,  Bromum,  Br  =  79.8.  This  element  is  found  in  sea- 
watex— and  many  mineral  waters,  chiefly  as  magnesium  bromide, 
which  compound,  however,  represents  in  all  these  waters  a  compar- 
atively small  percentage  of  the  total  quantity  of  the  different  salts 
present.  Most  of  these  salts  are  separated  from  the  water  by  evapo- 
ration and  crystallization,  and  the  remaining  mother-liquor,  contain- 
ing the  magnesium  bromide,  is  treated  with  chlorine,  which  liberates 
bromine,  the  vapors  of  which  are  condensed  in  cooled  receivers : 

MgBr2     -f     2C1    =    MgCl2     +     2Br. 

Bromine  is  at  common  temperature  a  heavy,  dark  reddish-brown 
liquid,  giving  off  yellowish-red  fumes  of  an  exceedingly  suffocating 
and  irritating  odor ;  it  is  very  volatile,  freezes  at  about  — 24°  C. 
( — 11°  F.),  and  has  a  specific  gravity  of  2.99;  it  is  soluble  in  30 
parts  of  water,  more  freely  in  alcohol,  abundantly  in  ether  and  bisul- 
phide of  carbon ;  it  is  a  strong  disinfectant,  and  its  aqueous  solution 
is  also  a  bleaching  agent. 

Hydrobromic  acid,  Acidum  hydrobromicum,  HBr  =  80.8. 
This  acid  cannot  well  be  obtained  by  the  action  of  concentrated  sul- 
phuric acid  upon  bromides,  since  the  hydrobromic  acid  first  formed 

QUESTIONS. — 151.  State  the  names  and  general  physical  and  chemical  prop- 
erties of  the  four  halogens.  152.  How  is  chlorine  found  in  nature,  and  why 
does  it  not  occur  in  a  free  state  ?  153.  State  the  general  principle  for  liberating 
chlorine  from  hydrochloric  acid,  and  explain  the  action  of  the  latter  on  man- 
ganese dioxide.  154.  Mention  of  chlorine :  its  atomic  weight,  molecular  weight, 
valence,  color,  odor,  action  when  inhaled,  and  solubility  in  water.  155.  How 
does  chlorine  act  chemically  upon  metals,  hydrogen,  phosphorus,  water,  am- 
monia, hydrocarbons,  and  coloring  matters  ?  156.  Mention  two  processes  for 
making  hydrochloric  acid ;  state  its  composition,  properties,  and  tests  by  which 
it  may  be  recognized.  157.  What  is  aqua  regia  ?  158.  State  the  composition 
of  hypochlorous  and  chloric  acids.  159.  What  is  the  difference  in  the  action 
of  chlorine  upon  a  solution  of  potassium  hydroxide  at  ordinary  temperature 
and  at  the  boiling-point?  160.  How  many  pounds  of  manganese  dioxide, 
and  how  many  of  hydrochloric  acid  gas  are  required  to  liberate  142  pounds  of 
chlorine  ? 


124  NON-METALS  AND  THEIR  COMBINATIONS. 

becomes  readily  decomposed  with  formation  of  sulphur  dioxide  and 
free  bromine.     Thus : 

2NaBr     -f     H2SO4    ;    =    2HBr    +     Na2SO4; 
2HBr      +     H2S04    =   =    2Br        +     SO2  +  2H2O. 

If,  however,  dilute  sulphuric  acid  is  added  to  a  warm  solution  of 
potassium  bromide,  potassium  sulphate  is  formed,  a  portion  of  which 
crystallizes  on  cooling.  From  the  remaining  portion  of  the  salt,  the 
hydrobromic  acid  may  be  separated  by  distillation. 

Hydrobromic  acid  may  also  be  obtained  by  the  formation  of  bromide  of 
phosphorus,  PBr5  (the  two  elements  combine  directly),  and  its  decomposition 
by  water : 

PBr5    +    4H2O    =    5HBr    +    H3PO4. 

In  the  form  of  solution  this  acid  may  be  prepared  also  by  treating  bromine 
under  water  with  hydrosulphuric  acid  until  the  brown  color  of  bromine  has 
entirely  disappeared.  The  reaction  is  as  follows : 

lOBr  +  2H2S  -f-  4H20  =  lOHBr  +  H2SO4  +  S. 

The  liquid  is  filtered  from  the  sulphur  and  separated  from  the  sulphuric  acid 
by  distillation. 

Hydrobromic  acid  is,  like  hydrochloric  acid,  a  colorless  gas,  of 
strong  acid  properties,  easily  soluble  in  water. 

Diluted  hydrobromic  add,  Acidum  hydrobromicum  dilutum,  is  a  solu- 
tion of  10  per  cent,  of  hydrobromic  acid  in  water.  It  is  a  colorless, 
odorless,  acid  liquid  of  the  specific  gravity  1.077. 

Hypobromic  acid,  HBrO ;  Bromic  acid,  HBrO3,  and  their  salts, 
the  hypobromites  and  bromates,  are  analogous  to  the  corresponding 
chlorine  compounds,  and  may  be  obtained  by  analogous  processes. 

Tests  for  Bromides. 
(Potassium  bromide,  KBr,  may  be  used.) 

1.  Silver  nitrate  produces  in  solutions  of  bromides  a  slightly  yel- 
lowish-white precipitate  of  silver  bromide,  insoluble  in  nitric  acid, 
sparingly  soluble  in  ammonium  hydroxide. 

2.  Addition  of  chlorine  water,  or  heating  with  nitric  acid,  liberates 
bromine,  which  may  be  dissolved  by  shaking  with  chloroform  or  ether. 

3.  Mucilage  of  starch  added  to  the  liberated  bromine  is  colored 
yellow. 

4.  A  crystal  of  potassium  bromide  dropped  into  an  acidified  solu- 
tion of  cupric  sulphate  produces  a  deep  red-brown  coloration  of  cupric 
bromide,  CuBr2. 

5.  Strong  sulphuric  acid  added  to  a  dry  bromide  liberates  hydro- 


BR  OMINE— IODINE— FL  UORINE.  125 

bromic  acid,  HBr,  a  portion  of  which  decomposes  with  liberation  of 
yellowish-red  vapors  of  bromine.     See  explanation  above. 

Iodine,  lodum,  I  =  126.53.  Iodine  is  found  in  nature  in  com- 
bination with  sodium  and  potassium,  in  some  spring  waters  and  in 
sea-water,  from  which  latter  it  is  taken  up  by  sea-plants  and  many 
aquatic  animals.  Iodine  is  derived  chiefly  from  the  ashes  of  sea- 
weeds known  as  Mp.  By  washing  these  ashes  with  water,  the  soluble 
constituents  are  dissolved,  the  larger  quantities  of  sodium  chloride, 
sodium  and  potassium  carbonates  are  removed  by  evaporation  and 
crystallization,  and  from  the  remaining  mother-liquor  iodine  is  ob- 
tained by  treating  the  liquor  with  manganese  dioxide  and  hydro- 
chloric (or  sulphuric)  acid : 

2KI  +  Mn02  +  2H2S04  =  K2SO4  -f  MnSO,  +  2H2O  +  21. 

The  liberated  iodine  distils,  and  is  collected  in  cooled  receivers. 
Sodium  nitrate  found  in  Chili  contains  a  small  quantity  of  sodium 
iodate,  and  the  mother-liquors,  from  which  the  nitrate  has  been  crys- 
tallized, contain  enough  iodate  to  be  employed  for  the  preparation  of 
iodine. 

Iodine  is  a  bluish-black,  crystalline  substance  of  a  somewhat 
metallic  lustre,  a  distinctive  odor,  a  sharp  and  acrid  taste,  and  a  neu- 
tral reaction.  Specific  gravity  4.948  at  17°  C.  (62.6°  F.).  It  fuses 
at  114°  C.  (237°  F.),  and  boils  at  180°  C.  (356°  F.),  being  converted 
into  beautiful  purple- violet  vapors ;  also,  it  volatilizes  in  small  quanti- 
ties at  ordinary  temperature.  It  is  soluble  in  about  5000  parts  of 
water,  more  soluble  in  water  containing  salts,  for  instance,  potassium 
iodide;  it  is  soluble  in  10  parts  of  alcohol  (tincture  of  iodine),  very 
soluble  in  ether,  bisulphide  of  carbon,  and  chloroform.  The  solution 
of  iodine  in  alcohol  or  ether  has  a  brown,  the  solution  in  disulphide 
of  carbon  or  in  chloroform  a  violet  color.  Iodine  stains  the  skin 
brown,  and  when  taken  internally  acts  as  an  irritant  poison. 

Hydriodic  acid,  Hydrogen  iodide,  HI.  This  is  a  colorless  gas 
readily  soluble  in  water ;  the  solution  is  unstable,  being  easily  decom- 
posed with  liberation  of  iodine.  It  may  be  obtained  by  processes 
analogous  to  those  mentioned  for  the  preparation  of  hydrobromic 
acid.  The  action  of  hydrosulphuric  acid  upon  iodine  in  the  presence 
of  water  is  as  follows  : 

H2S    +    21       :    2HI    +    S. 

Another  method  depends  on  the  decomposition  of  an  aqueous  so- 
lution of  potassium  iodide  by  an  alcoholic  solution  of  tartaric  acid. 


126  NON-METALS  AND  THEIR  COMBINATIONS. 

Upon  cooling   the   mixture  to   the   freezing-point,   acid   potassium 
tartrate  separates,  while  hydriodic  acid  remains  in  solution  : 
KI     +    H2C4H4O6    :       KHC4H4O6    +    HI. 

Whilst  hydriodic  acid  itself  is  not  of  much  importance,  many  of 
its  salts,  the  iodides,  are  of  great  interest. 

Tests  for  iodine  and  iodides. 
(Potassium  iodide,  KI,  may  be  used.) 

1.  Add  to  free  iodine  (or  to  an  iodide,  after  it  has  been  decomposed 
by  a  few  drops  of  chlorine  water,  or  by  strong  nitric  acid)  mucilage  of 
starch  :  a  dark-blue  color  is  produced,  due  to  the  formation  of  "  blue 
iodized  starch." 

2.  From  solution  of  an  iodide  liberate  iodine  by  adding  chlorine 
water,  or  nitric  acid  containing  a  little  nitrous  acid,  and  shake  the 
solution  with  disulphide  of  carbon  or  chloroform.     After  standing  a 
few  minutes  the  liquids  form  a  layer  of  a  beautiful  violet  color. 

3.  Add  to  solution  of  an  iodide,  solution  of  silver  nitrate :  a  pale 
yellow  precipitate  of  silver  iodide,  Agl,  falls,  which  is  insoluble  in 
nitric  acid,  and  sparingly  soluble  in  dilute  ammonium  hydroxide. 

4.  Add  lead  acetate  to  a  neutral  solution  of  an  iodide :  a  yellow 
precipitate  of  lead 'iodide,  PbI2,  is  produced. 

5.  Add  mercuric  chloride  to  a  neutral  solution  of  an  iodide:  a  red 
precipitate  of  mercuric  iodide,  HgI2,  is  produced. 

6.  Add  sulphuric  acid :  violet  vapors  of  iodine  are  evolved. 

lodic  acid,  HI03.  When  iodine  is  dissolved  in  strong  nitric  acid,  this  solu- 
tion being  then  evaporated  to  dryness  and  heated  to  about  200°  C.  (392°  F.) 
a  white  residue  remains,  which  is  iodine  pentoxide : 

61  +  10HN03  =  5N2O2  +  5H2O  +  3I2O5. 
By  dissolving  this  oxide  in  water,  iodic  acid  is  obtained : 
I205  +  H20  =  2HI03. 

Iodic  acid  is  a  white  crystalline  substance,  very  soluble  in  water.  From 
iodic  acid  or  from  iodates,  sulphurous  acid  and  many  other  reducing  agents 
liberate  iodine. 

Sulphur  iodide,  Sulphuris  iodidum,  S2I2.  When  the  two  elements,  sulphur 
and  iodine,  are  mixed  together  in  the  proportion  of  their  atomic  weights,  and 
this  mixture  is  heated,  direct  combination  takes  place.  The  fused  mass  is 
grayish-black,  brittle,  has  a  crystalline  fracture  and  a  metallic  lustre.  It  is 
almost  insoluble  in  water,  but  soluble  in  glycerin  and  in  carbon  disulphide. 

Fluorine,  F  =  19.  This  element  is  found  in  nature,  chiefly  as 
fluorspar,  calcium  flouride,  CaF2;  traces  of  fluorine  occur  in  many 


BROMINE—  IODINE-FLUORINE.  127 

minerals,  in  some  waters,  and  also  in  the  enamel  of  teeth,  and  in  the 
bones  of  mammals.  Fluorine  was,  until  1887,  scarcely  known  in  the 
elementary  state,  because  all  attempts  to  isolate  it  were  frustrated  by 
the  powerful  affinities  which  this  element  possesses,  and  which  render 
it  difficult  to  obtain  any  material  (from  which  a  vessel  may  be  made) 
which  is  not  chemically  acted  upon,  and,  therefore,  destroyed,  by 
fluorine.  The  method  used  now  for  liberating  fluorine  depends  upon 
the  decomposition  of  hydrofluoric  acid  by  a  strong  current  of  electricity 
in  an  apparatus  constructed  of  platinum  with  stoppers  of  fluorspar. 
To  prevent  too  rapid  corrosion  of  the  platinum  vessels,  the  decom- 
position is  accomplished  at  a  temperature  below  the  freezing-point. 
Fluorine  is  a  gas  of  yellowish  color,  having  a  highly  irritating  and 
suffocating. odor,  and  possessing  affinities  stronger  than  those  of  any 
other  element.  As  a  supporter  of  cojabustion,  fluorine  leaves  oxygen 
far  behind  ;  it  combines  sp&j^ajgteously  even  in  the  dark  and  at  low 
temperature  with  hydrogen ;  sulphur,  phosphorus,  lampblack,  and 
also  many  metals  ignite  readily  in  fluorine ;  even  the  noble  metals, 
gold,  platinum,  and  mercury,  are  converted  into  fluorides;  from 
sodium  chloride  the  chlorine  is  liberated  with  the  formation  of 
sodium  fluoride ;  organic  substances,  such  as  oil  of  turpentine,  alco- 
hol, ether,  and  even  cork  ignite  spontaneously  when  brought  in 
contact  with  this  remarkable  element. 

Hydrofluoric  acid,  HP  (Hydrogen  fluoride).  A  colorless  gas,  very 
irritating,  soluble  in  water.  It  is  obtained  by  the  action  of  sulphuric 
acid  on  fluorspar  : 

CaF2    -f    H2SO4    =    2HF    -f     CaSO4. 

Hydrofluoric  acid,  either  in  the  gaseous  state  or  its  solution  in 
water,  is  used  for  etching  on  glass.  This  effect  is  due  to  the  action  of 
the  acid  upon  the  silica  of  the  glass,  which  is  converted  into  either 
silicon  fluoride,  SiF4;  or  into  hydrofluosilicic  acid,  H2SiF6. 

Hydrofluoric  acid,  or  strong  solutions  of  it,  are  powerful  antiseptics.  In 
small  quantities  the  acid  is  used  as  an  admixture  to  fermenting  liquids,  as  it 
has  been  found  that  it  does  not  act  upon  the  principal  ferment  of  yeast,  which 
causes  the  decomposition  of  sugar  into  alcohol  and  carbon  dioxide,  while  it 
readily  destroys  a  number  of  objectionable  ferments.  The  yield  of  alcohol  is 
thus  considerably  increased. 

Experiment  15.  Prepare  a  glass  plate  by  heating  it  slightly  and  covering  its 
surface  with  a  thin  layer  of  wax  or  paraffin ;  after  cooling,  scratch  some  letters 
or  figures  through  the  wax,  thus  exposing  the  glass.  Set  the  plate  over  a  dish 
(one  made  of  lead  or  platinum  answers  best),  in  which  a  few  grammes  of  pow- 
dered fluorspar  have  been  mixed  with  about  an  equal  weight  of  sulphuric  acid, 


128  NON-METALS  AND  THEIR  COMBINATIONS. 

and  set  in  the  open  air  for  a  few  hours  (heating  slightly  facilitates  the  action) ; 
upon  removing  the  wax  or  paraffin,  the  glass  will  be  found  to  be  etched  where 
its  surface  was  exposed  to  the  vapors  of  the  acid.  This  experiment  serves  also 
as  the  best  test  for 


QUESTIONS. — 161.  How  is  bromine  found  in  nature?  162.  State  the  physical 
and  chemical  properties  of  bromine.  163.  What  is  hydrobromic  acid,  and  how 
can  it  be  made?  164.  By  what  tests  may  bromine  and  bromides  be  recognized? 
165.  What  is  the  chief  source  of  iodine?  166.  What  are  the  chemical  and 
physical  properties  of  iodine  ?  167.  What  is  tincture  of  iodine,  what  is  its 
color,  and  how  does  it  stain  the  skin?  168.  Mention  reactions  by  which 
iodine  and  iodides  may  be  recognized.  169.  By  what  element  may  bromine 
and  iodine  be  liberated  from  their  compounds  ?  170.  How  is  hydrofluoric  acid 
made,  and  what  is  it  used  for  ? 


IV. 
METALS  AND  THEIR  COMBINATIONS. 


18.  GENEEAL  REMARKS  REGARDING  METALS. 

OF  the  total  number  of  fifty-five  metallic  elements  only  about 
one-half  are  of  sufficient  general  interest  and  importance  to  deserve 
consideration  in  this  book. 

Derivation  of  names,  symbols,  and  atomic  weights. 

Aluminum,         Al    =    27.04.     From  alum,  a  salt  containing  it. 
Antimony,          Sb    =  119.6.       From  the  Greek  avrl,  (anti),  against,  and  moine,  a 
(Stibium.)  French  word  for  monk,  from  the  fact  that  some 

monks  were  poisoned  by  compounds  of  antimony. 

Stibium,  from  the  Greek,  crifii  (stibi),  the  name 

for  the  native  sulphide  of  antimony. 
Arsenicum,         As    =     74.9.       From  the  Greek  apoevmbv  (arsenicon),  the  name  for 

the  native  sulphide  of  arsenic. 
Barium,  Ba    =136.9.       From  the  Greek  papvs  (barys),  heavy,  in  allusion  to 

the  high  specific  gravity  of  barium  sulphate,  or 

heavy -spar. 
From  the  German  wismuth,  an  expression  used  long 

ago  by  the  miners  in  allusion  to  the  variegated 

tints  of  the  metal  when  freshly  broken. 
From  the  Greek  nadfieia  (kadmeia)  the  old  name  for 

calamine  (zinc  carbonate),  with  which  cadmium 

is  frequently  associated. 

Calcium,  Ca    =    39.91.     From  the  Latin  calx,  lime,  the  oxide  of  calcium. 

Chromium,         Cr    =    52.0.       From  the  Greek  XP^f10-  (chroma),  color,  in  allusion 

to  the  beautiful  colors  of  all  its  compounds. 
Cobalt,  Co    =     58.6.       From  the  German  Kobold,  which  means  a  demon 

inhabiting  the  mines. 
Copper,  Cu   =     63.18      From  the  Latin  cuprum,  copper,  and  this  from  the 

Island  of  Cyprus,  where  copper  was  first  obtained 

by  the  ancients. 
Gold,  Au  =  196.7.       Gold  means  bright  yellow  in  several  old  languages. 

(Aurum.)  The  Latin  aurum  signifies  the  color  of  fire. 

Iron,  Fe    =     55.88.     Iron  probably  means  metal ;  the  derivation  of  the 

Latin  ferrum  is  not  definitely  known. 

9  (129) 


Bismuth,  Bi    =  208.9. 

Cadmium,          Cd   =  111.5. 


130 


METALS  AND  THEIE  COMBINATIONS. 


Lead,  Pb 

(Plumbum.) 

Lithium,  Li 

Magnesium,  Mg 


=  206.4.       Both  words  signify  something  heavy. 


7.0], 
24.3. 

54.8. 
199.8. 


Mercury,  Hg 

(Hydrargyrum  ) 

Molybdenum,    Mo 

Nickel,  Ni 


Platinum,  Pt    =  194.3. 

39.03. 


Potassium,         K 
(Kalium.) 

Silver,  Ag 

(Argentum.) 

Sodium,  Na 

(Natrium.) 


107.66. 
23.0. 


Strontium,  Sr  =    87.3. 

Tin,  Sn  =  118.8. 

(Stannum.) 

Zinc,  Zn  =    65.1. 


From  the  Greek  M6eio<;  (litheios),  stony. 
From  Magnesia,  a  town  in  Asia  Minor,  where  mag- 
nesium carbonate  was  found  as  a  mineral. 
Probably  from  magnesium,  with  the  compounds  of 

which  it  was  long  confounded. 
From  Mercury,  the  messenger  of  the  Greek  gods. 

Hydrargyrum  means  liquid  silver. 
From  the  Greek  nohvfidog  (molybdos),  lead. 
From  the  old   German   word  nickel,  which  means 

worthless. 
Platina  is  the  diminutive  of  the  Spanish  word  plata, 

silver. 
From  pot-ash ;  potassium  carbonate  being  the  chief 

constituent  of  the  lye  of  wood-ashes.     Kali  is  the 

Arabic  word  for  ashes. 
Both  words  signify  white. 

From  soda-ash,  or  sod-ash,  the  ashes  of  marine  plants 
which  are  rich  in  sodium  carbonate.  Natron  is  an 
old  name  for  natural  deposits  of  sodium  carbonate. 

From  Strontian,  a  village  in  Scotland,  where  stron- 
tium carbonate  is  found. 

Both  words  most  likely  signify  stone. 

Most  likely  from  the  German  zinn  or  tin,  the  metals 
having  been  confounded  with  each  other. 


Melting-points  of  metals. 


Fusible  below  the   f  Mercury 
boiling-point  of  •{  Potassium 

.,..4  ..  I  Qj"is3   ?11WV* 


water, 


Fusible  below  red 
heat, 


Unknown, 


[  Sodium 
f  Lithium    . 
|  Tin    .        . 

Cadmium  . 

Bismuth     . 

Lead 

Zinc  . 

Magnesium 

Antimony 

Aluminum 

Barium. 

Calcium. 

Strontium. 

Arsenic. 


c. 

F. 

.  —40° 

—  40° 

.  +62 

+144 

.   97 

207 

.  180 

356 

.  228 

443 

.  230 

446 

.  260 

500 

.  325 

617 

.  412 

773 

.  455 

850 

.  620 

1150 

,  700 

1292 

TIME  OF  DISCOVERY  OF  THE  METALS. 


131 


'  Silver 

Copper 

Gold 

Cast-iron  . 

Pure  iron, 

Infusible  below  a 

Nickel, 

red  heat, 

Cobalt, 

Manganese, 

Molybdenum,     -» 

Chromium,         j 

Platinum, 


1020  1868 

1100  2012 

1200  2192 

1800  3272 


Highest  heat  of  forge. 


V  Agglomerate,  but  do  not  melt  in  forge. 

f  Fusible  in  the  oxyhydrogen  blowpipe 
I      flame. 


Specific  gravities  of  metals  at  15.5°  C, 


Lithium 

.     0.593 

Potassium 

.    0.865 

Sodium 

.    0.972 

Calcium 

.     1.57 

Magnesium  . 
Strontium 

.    1.75 
.    2.54 

Aluminum     . 

.    2.67 

Barium 

.    4.00 

Arsenic 

.    5.88 

Antimony 
Zinc 
Tin 

.     6.72 
.    6.90 
.    7.29 

Iron 

.    7.79 

Manganese 
Molybdenum    . 
Cadmium 

.    8.00 
.    863 
.    870 

Nickel      . 

.    870 

Cobalt 

.    8.95 

Copper     . 
Bismuth    . 

.    896 
.    990 

Silver 

.  10.50 

Lead 

.  11.36 

Mercury  . 
Gold 

.  1359 
.  19.36 

Platinum  . 

.  21.50 

Time  of  discovery  of  the  metals. 


Gold, 

Silver, 

Mercury, 

Copper, 

Zinc, 

Tin, 

Iron, 

Lead, 

Antimony, 

Bismuth, 

Arsenic, 

Cobalt, 

Platinum, 

Nickel, 

Manganese, 

Molybdenum, 

Chromium, 


These  metals  were  known  to  the  ancients,  because 
either  they  are  found  in  a  metallic  state,  or  can  be 
obtained  by  comparatively  simple  processes  from 
the  oxides. 


>  Latter  part  of  the  fifteenth  century. 


1694,  by  Schroder. 
1733,  by  Brandt. 
1741,  by  Wood. 
1751,  by  Cronstedt. 
1774,  by  Galm 
1782,  by  Hjelrn. 
1797,  by  Vauquelin. 


132 


METALS  AND  THEIR  COMBINATIONS. 


Potassium, 

Sodium, 

f   H 

Barium, 
Calcium, 

1807-1808 

Strontium, 

Magnesium,     J 

Cadmium,            1817,  by  Stromeyer. 

Lithium,              1817,  by  Arfvedson. 

Aluminum,          1828,  by  Wohler. 

H.  Davy  discovered  methods  for  the 
separation  of  these  metals  from 
their  oxides. 


Valence  of  metals. 


Univalent. 

Lithium, 

Potassium, 

Sodium, 

Silver. 

Bivalent. 

Barium, 

Calcium, 

Strontium, 

Magnesium, 

Cadmium, 

Zinc, 

Copper, 

Mercury. 

Trivalent. 
Aluminum, 
Bismuth, 
Gold. 


Sexivalent. 
Molybdenum. 


Bi-  and  sexivalent. 
Chromium, 
Cobalt, 
Iron, 


Nickel. 

Bi-  and  quadrivalent 
Lead, 
Platinum, 
Tin. 


Tri-  and  quinquivalent. 
Antimony, 
Arsenic. 


Occurrence  in  nature. 

a.  In  a  free  or  combined  state. 

|  Almost  exclusively  in  the  metallic  state. 
Platinum, 

Silver,  I   Ag  metalg  Qr  gulphides. 

Mercury, 

Bismuth,  generally  metallic,  also  as  oxide  and  sulphide. 

Copper,  rarely  metallic ;  chiefly  as  sulphide,  oxide,  and  carbonate. 

6.  In  combination  only. 

Potassium, 

Sodium,  \  Chiefly  as  chlorides  or  silicates. 

Lithium, 


CLASSIFICATION  OF  METALS. 


133 


Barium,  as  sulphate 

Calcium,  \ 

Strontium,         I  As  carbonates,  sulphates,  silicates. 

Magnesium, 

Aluminum,  in  silicates. 

Iron,  \ 

Zinc,  [•  As  oxides,  carbonates,  sulphides. 

Cadmium, 

Arsenic, 

Antimony, 

Lead,  I  chiefly  M  suiphides. 

Cobalt, 

Nickel, 

Molybdenum,  J 

Chromium,       ^ 

Manganese,       >  Chiefly  as  oxides. 

Tin, 

Classification  of  metals. 


Light  metals. 

Sp.  gr.  from  0.6  to  4. 

Sulphides  soluble  in  water. 

Light  metals. 

Alkaline  earth  metals. 

Ba,  Ca,  Sr,  (Mg). 

Oxides  soluble ; 


Heavy  metals. 

Sp  gr.  from  6  to  21.5. 

Sulphides  insoluble  in  water 


Earth  metals. 

Al,  and  many  rare  metals. 
Oxides  insoluble. 


Arsenic  group. 
As,  Sb,  Sn,  Au,  Pt,  Mo. 


Carbonates  insoluble. 

Heavy  metals. 

Lead  group. 
Pb,  Cu,  Bi,  Ag,  Hg,  Cd. 


Sulphides  insoluble  in  dilute  acids. 


Alkali-metal. 

K,  Na,  Li,  (NHJ. 

Oxides,  carbonates,  and 

most  salts  soluble. 


Iron  group. 

Fe,  Co,  Ni,  Mn,  Zn,  Cr. 

Sulphides  soluble  in 

dilute  acids. 


Sulphides  soluble  in  am- 
monium sulphide. 


Sulphides  insoluble  in 
ammonium  sulphide. 


Properties  of  metals.  All  metals  have  a  peculiar  lustre  known 
as  metallic  lustre,  and  all  are  good  conductors  of  heat  and  electricity. 
The  color  of  most  metals  is  white,  grayish,  or  bluish-white,  or  dark- 
gray  ;  a  few  metals  show  a  distinct  color,  as,  for  instance,  gold  and 
calcium  (yellow),  and  copper  (red). 

At  ordinary  temperatures  metals  are  solids  with  the  exception  of 
mercury,  all  are  fusible,  and  some  are  so  volatile  tliat  they  may  be 
(Jistilled^  Most,  probably  all,  metals  may  be  obtained  in  a  crystal- 
lized condition. 

The  combinations  of  metals  among  themselves  are  called  alloys,  or, 
when  mercury  is  one  of  the  constituents,  amalgams.  These  combina- 


134  METALS  AND  THEIR  COMBINATIONS. 

tions,  which  usually  may  be  obtained  by  fusing  the  metals  together, 
must  be  looked  upon  as  molecular  mixtures,  not  as  definite  chemical 
compounds.  All  alloys  still  exhibit  the  metallic  nature  in  their 
general  physical  characters.  It  is  different,  however,  when  metals 
combine  with  non-metals  ;  in  this  case  the  metallic  characters  are 
lost  almost  invariably. 

All  metals  combine  with  chlorine,  fluorine,  and  oxygen;    most 
metals  also  with  sulphur,  bromine,  and  iodine,  forming  the  respective 
chlorides,  fluorides,  oxides,  sulphides,  bromides,  and  iodides.     Metals 
replace  hydrogen  in  acids,  forming  salts. 
r   Most  metals  may  be  obtained  from  their  oxides  by  heating  the 

/latter  with  charcoal,  the  carbon  combining  with  the  oxygen  of  the 

/  oxide,  whilst  the  metal  is  liberated  : 

MO  +  C  =  CO    +    M; 
or 

2MO  +  C  =  CO2  +  2M. 

Also  hydrogen  may  be  used  in  some  cases  as  the  deoxidizing  agent  : 
MO  +  2H  =  H20  -f  M. 

Some  metals  are  found  in  nature  chiefly  as  sulphides,  which  usually 
are  converted  into  oxides  (before  the  metal  can  be  obtained)  by  roast- 
ing. The  term  roasting,  when  used  in  metallurgy,  means  heating 
strongly  in  an  oxidizing  atmosphere,  when  the  sulphides  are  con- 
verted into  sulphates  or  oxides,  thus  : 

MS  +  4O  =  MSO4; 
or 

MS  +  3O  =  MO  +  SO2. 

19.    POTASSIUM  (KALIUM). 

K1  =  39  (39  03). 

General  remarks  regarding-  alkali-metals.  The  metals  potas- 
sium, sodium,  lithium  (rubidium  and  csesium)  form  the  group  of  the 

~ 


QUESTIONS.  —  171.  How  many  metals  are  known,  and  about  how  many  are 
of  general  interest?  172.  Mention  some  metals  having  very  low  and  some 
having  very  high  fusing-points.  173.  What  range  of  specific  gravities  do  we 
find  among  the  metals?  174.  Mention  some  univalent  and  some  bivalent 
metals  ;  also  some  which  show  a  different  valence  under  different  conditions. 
175.  Mention  some  metals  which  are  found  in  nature  in  an  uncombined  state  ; 
some  which  are  found  as  oxides,  sulphides,  chlorides,  and  carbonates,  respec- 
tively. 176.  Into  what  two  groups  are  the  metals  divided?  177.  State  the 
three  groups  of  light  metals  ?  178.  What  is  a  metal  ?  179.  What  is  an  alloy, 
and  what  an  amalgam?  180.  By  what  process  can  most  metals  be  obtained 
from  their  oxides  ? 


POTASSIUM.  135 

alkali-metals?  which,  in  many  respects,  show  a  great  resemblance  to 
each  other  in  chemical  and  physical  properties.  For  reasons  to  be 
explained  hereafter,  the  compound  radical  ammonium  is  usually 
classed  among  the  alkali-metals. 

JThejilkali-metals  are  all  univalent^  they  decompose  water  at  the 
ordinary  temperature,  with  liberation  of  hydrogen;  they  combine 
spontaneously  with  oxygen  and  chlorine ;  their  hydroxides,  sulphates, 
nitrafes^  phosphates,  carbonates,  sulphides,  chlorides,  iodides,  and 
nearly  all  other  of  their  salts  are  soluble^  in  water ;  all  these  com- 
pounds  are  white,  solid  substances,  many  of  which  are  fusible  at  a 
red  heat.  Of  all  metals,  those  of  the  alkalies  are  the  only  ones  form- 
ing hydroxides  and  carbonates  which  are  not  decomposed  by  heat. 

The  metals  themselves  are  of  a  silver- white  color,  and  extremely 
soft;  on  account  of  their  tendency  to  combine  with  oxygen  they 
must  be  kept  in  a  liquid  not  containing  that  element  ^coal-oil)  or  in 
an  atmosphere  of  hydrogen. 

The  metals  may  be  obtained  by  heating  their  carbonates  with  carbon 
in  iron  retorts,  the  escaping  vapors  being  passed  under  coal-oil  for 
condensation  of  the  metal : 

K2CO3  +  20  =  SCO  4-  2K. 

Occurrence  in  nature.  Potassium  is  found  in  nature  chiefly  as  a 
double  silicate  of  potassium  and  aluminum  (granite  rocks,  feldspar, 
and  other  minerals),  or  as  chloride  and  nitrate.  By  the  gradual  dis- 
integration of  the  different  granite  rocks  containing  potassium  silicate, 
this  has  entered  into  the  soil,  whence  it  is  taken  up  by  plants  as  one 
of  the  necessary  constituents  of  their  food. 

In  the  plant  potassium  enters  largely  into  combination  with  organic 
compounds  (tartaric  acid,  citric  acid,  etc.),  and  when  the  plant  is 
burned,  ashes  are  left  containing  the  potassium,  now  in  the  form  of 
carbonate.  By  washing  such  ashes  (chiefly  wood  ashes)  with  water 
and  filtering,  the  insoluble  matter  (carbonates,  phosphates,  and  sul- 
phates of  calcium  and  magnesium,  silica,  etc.)  is  left  behind,  whilst  a 
,lye  is  "Obtained  containing  the  soluble  constituents,  of  which  potassium 
carbonate  is  the  principal  one,  chlorides  and  sulphates  of  potassium 
and  sodium  also  being  present  in  small  quantities. 

/     By  evaporation  of  this  lye  to  dryness  an  impure  potassium  car- 

[  bonate  is  obtained,  which  is  sold  as  crjj^e  potash. 

^  Up  to  within  twenty-five  years  ago  the  chief  supply  of  potash  was 
obtained  by  this  process,  and  the  trees  of  thousands  cf  acres  were 
burned  with  the  view  of  obtaining  potash.  To-day  this  mode  of 


136  METALS  AND  THEIR  COMBINATIONS. 

manufacturing  potash  is  very  limited,  and  is  rapidly  decreasing,  as, 
fortunately,  an  almost  unlimited  supply  of  soluble  potassium  salts  is 
furnished  by  the  salt-mines  of  Stassfurt,  Germany,  where  large  quan- 
tities of  potassium  chloride  (combined  or  mixed  with  the  chlorides 
and  sulphates  of  sodium,  magnesium,  calcium,  and  other  salts)  are 
found,  from  which  the  carbonate  and  other  salts  are  manufactured. 

/  Potassium  hydroxide.  Potassium  hydrate,  Potassa,  KOH=56 
(^Caustic  potash),  may  be  Attained  by  the  action  of  the  metal  on  water : 

+  H2O  =  H  +  KOH. 
The  usilal process  for  making  potassium  hydroxide  is  to  boil  together 
a  dilute  solution  of  potassium  carbonate  or  bicarbonate  and  calcium 

hydroxide : 

K2CO3  +  Ca(OH)2  ==  CaCO3  -f  2KOH. 

Experiment  16.  Add  gradually  5  grammes  of  calcium  hydroxide  (slaked 
lime)  to  a  boiling  solution  of  about  5  grammes  of  potassium  carbonate  in  50 
c.c.  of  water,  and  continue  to  boil  until  the  conversion  of  potassium  carbonate 
into  hydroxide  is  complete.  This  can  be  shown  by  filtering  off  a  few  drops  of 
the  liquid,  and  supersaturating  with  dilute  hydrochloric  acid,  which  should  not 
cause  effervescence.  Set  aside  to  cool,  and  when  all  solids  have  subsided,  pour 
off  the  clear  solution  of  potassium  hydroxide,  which  may  be  used  for  Experi- 
ment 17.  What  quantities  of  K2CO3  and  Ca(OH)2  are  required  to  make  one  liter 
of  a  5  per  cent,  solution  of  potassium  hydroxide  ? 

Potassium  hydroxide  is  a  white,  hard,  highly  deliquescent  sub- 
stance, soluble  in  0.5  part  of  water  and  2  parts  of  alcohol ;  it  fuses 
at  a  low  red  heat,  forming  an  oily  liquid,  which  may  be  poured  into 
(suitable  moulds  to  form  pencils ;  at  a  strong  red  heat  it  is  slowly 
Volatilized  without  decomposition ;  it  is  strongly  alkaline  and  a 
powerful  base,  readily  combining  with  all  acids  ;  itrajjidl^jlsairoys 
organicjiggiies,,  and  when  taken  internally  acts  as  a  powerful  corrosive, 
and  most  likely  otherwise  as  a  poison 

Antidotes :  dilute  acids,  vinegar,  to  form  salts ;  or  fat,  oil,  or  milk, 
to  form  soap. 

Liquor  potassce  is  a  5  per  cent,  solution  of  potassium  hydroxide 
in  water. 

Potassa  with  lime  is  a  mixture  of  equal  parts  of  potassium  hydroxide 
and  calcium  oxide. 

Potassium  oxide,  K2O.  This  compound  can  be  obtained  either 
by  burning  potassium  in  air  and  subsequent  heating  of  the  product 
to  a  high  temperature,  or  by  fusing  together  potassium  hydroxide 
and  metallic  potassium  : 

2KOH  +  2K  =  2K20  +  2H 


POTASSIUM.  137 

Besides  this  potassium  monoxide,  corresponding  to  water  in  its 
composition,  two  other  oxides  of  the  composition  K2O2  (corresponding 
to  hydrogen  peroxide,  H2O2)  and  K2O4  are  known.  The  latter  oxide 
is  obtained  by  the  combustion  of  potassium  in  oxygen.  It  is  a  strong 
oxidizing  agent,  and  at  a  high  temperature  is  decomposed  into  oxide 
and  oxygen. 

Potassium  carbonate,  Potassii  carbonas,  K2CO3  =  138,  is  ob- 
tained from  wood-ashes  in  an  impure  state  as  described  above,  or 
from  the  native  chloride  by  the  so-called  Leblanc  process,  which  will 
be  described  in  connection  with  sodium  carbonate.  Crude  potash 
when  calcined  in  a  furnace  until  white  is  known  as  pearlash. 

Pure  potassium  carbonate  is  obtained  by  heating  the  bicarbonate, 
which  is  decomposed  as  follows  : 

2KHC03  =  K2C03  +  H2O  -f  CO2. 

Potassium  carbonate  is  deliquescent,  is  soluble  in  about  an  equal 
weight  of  water,  insoluble  in  alcohol,  and  has  strong  basic  and  alka- 
line properties. 

Potassium  bicarbonate,  Potassii  bicarbonas,  KHCO3  =  10O. 
Obtained  by  passing  carbon  dioxide  through  a  strong  solution  of 
potassium  carbonate,  when  the  less  soluble  bicarbonate  forms  and 
separates  into  crystals  : 

K2C03  +  H2O  +  CO2  =  2KHCO3. 

Potassium  nitrate,  Potassii  nitras,  KNO3=101  (Nitre,  Saltpetre). 
Potassium  and  sodium  nitrate  are  found  as  an  incrustation  upon  and 
throughout  the  soil  of  certain  localities  in  dry  and  hot  countries,  as, 
for  instance,  in  Peru,  Chili,  and  India.  The  formation  of  these 
nitrates  is  to  be  explained  by  the  absorption  of  ammonia  by  the  soil, 
where  it  gradually  is  oxidized  and  converted  into  nitric  acid.  This 
nitrification,  i.  e.,  the  conversion  of  ammonia  into  nitric  acid,  seems  to 
be  due  largely  to  the  action  of  micro-organisms  termed  the  nitrifying 
ferment.  The  acid  after  being  formed  combines  with  the  strongest 
base  present  in  the  soil.  If  this  base  be  potash,  potassium  nitrate 
will  be  formed  ;  if  soda,  sodium  nitrate ;  if  lime,  calcium  nitrate. 

Upon  the  same  principle  is  based  the  manufacture  "of  nitre  on  a 
large  scale,  which  is  accomplished  by  mixing  animal  refuse  matter 
with  earth  and  lime,  and  placing  the  mixture  in  heaps  under  a  roof, 
to  prevent  lixiviation  by  rain.  By  decomposition  (putrefaction)  of 
the  animal  matter,  ammonia  is  formed,  which,  by  oxidation,  is  con- 
verted into  nitric  acid,  which  then  combines  with  the  calcium  of  the 


138  METALS  AND  THEIR  COMBINATIONS. 

lime,  forming  calcium  nitrate.     This  is  dissolved  in  water,  and  to 
the  solution  potassium  carbonate  (or  chloride)  is  added,  when  calcium 
carbonate  (or  chloride)  and  potassium  nitrate  are  formed  : 
Ca(NO3)2  +  K2CO3  =  2KNO3  +  CaCO3 

Large  quantities  of  potassium  nitrate  are  made  also  by  decompos- 
ing sodium  nitrate  (Chili  saltpetre)  by  potassium  chloride : 
NaNO3  +  KC1  =  KN03  -f  NaCl. 

Potassium  nitrate  crystallizes  in  six-sided  prisms ;  it  is  soluble  in 
about  3.8  parts  of  cold,  and  0.4  part  of  boiling  water.  It  has  a  cool- 
ing, saline,  and  pungent  taste,  and  a  neutral  reaction.  When  heated 
with  deoxidizing  agents  or  combustible  substances,  these  are  readily 
oxidized. 

It  is  this  oxidizing  power  which  is  made  use  of  in  the  manufacture 
of  guxywwder — an  intimate  mixture  of  potassium  nitrate,  sulphur, 
and  carbon."  Upon  heating  or  igniting  the  gunpowder,  the  sulphur 
and  carbon  are  oxidized,  a  considerable  quantity  of  various  gases 
(CO,  CO2,  N,  SO^petcT)  being  formed,  the  sudden  generation  and 
expansion  of  which  cause  the  explosion. 

Potassium  chlorate,  Potassii  chloras,  KC1O3  =  122.4  (Chlorate 
of  potassium),  may  be  obtained  by  the  action  of  chlorine  on  a  boiling 
solution  of  potassium  hydroxide  : 

6C1  +  6KOH  ==  5KC1  +  KC1O3  +  3H2O. 

A  cheaper  process  for  the  manufacture  of  potassium  chlorate  is  the 
action  of  chlorine  upon  a  boiling  solution  of  potassium  carbonate,  to 
which  calcium  hydroxide  has  been  added  : 

K2C03  +  6(Ca2OH)  +  12C1  =  2KC1O3  +  CaCO3  +  5CaCl2  +  6H2O. 

Potassium  chlorate  crystallizes  in  white  plates  of  a  pearly  lustre ; 
it  is  soluble  in  16.7  parts  of  cold,  and  1.7  parts  of  boiling  water.  It 
is  even  a  stronger  oxidizing  agent  than  potassium  nitrate,  for  which 
reason  care  must  be  taken  in  mixing  it  with  organic  matter  or  other 
deoxidizing  agents,  or  with  strong  acids,  which  will  liberate  chloric 
acid.  When  heated  by  itself,  it  is  decomposed  into  potassium  chloride 
and  oxygen. 

Potassium  sulphate,  Potassii  sulphas,  K2SO4  — 174.  Obtained 
by  the  decomposition  of  potassium  chloride,  nitrate,  or  carbonate,  by 
sulphuric  acid : 

2KC1  +  H2SO4  =  2HC1  +  K2SO4; 
K2CO3  +  H2SO4  =  H2O  +  CO3 


POTASSIUM.  139 

Potassium  sulphate  exists  in  small  quantities  in  plants,  and  in 
nearly  all  animal  tissues  and  fluids,  more  abundantly  in  urine. 

Potassium  hydrogen  sulphate,  bisulphate,  or  potassium  add  sulphate, 
may  be  obtained  by  the  action  of  one  molecule  of  potassium  chloride 
upon  one  molecule  of  sulphuric  acid : 

KC1  +  H2S04  =  HC1  +  KHSO4. 

Potassium  sulphite.  Obtained  by  the  decomposition  of  potassium  carbonate 
by  sulphurous  acid : 

K2C03  +  H2S03  =  H20  +  C02  +  K2S03. 

Potassa  Sulphurata,  U.  S.  P.  (Sulphurated  potassa,  Liver  of  sulphur,  Hepar 
sulphuris}.  A  mixture  of  potassium  sulphide,  polysulphide,  and  thiosulphate. 
It  is  made  by  heating  a  mixtur^  of  one  part  of  sulphur  and  two  parts  of  potas- 
sium carbonate  in  a  covered  crucible,  and  pouring  the  fused  mass  on  a  marble 
slab: 

3K2C03  +  8S  =  K2S203  +  2K2S3  +  3CO2. 

The  freshly  prepared  substance  has  a  liver-brown  color,  turning  gradually  to 
greenish  yellow ;  it  is  very  apt  to  absorb  water  and  oxygen,  both  the  sulphide 
and  hyposulphite  becoming  oxidized,  and  finally  converted  into  sulphates. 

Potassium  hypophosphite,  Potassii  hypophosphis,  KPH2O2= 
104,  may  be  obtained  by  decomposing  a  solution  of  calcium  hypo- 
phosphite  by  potassium  carbonate : 

Ca(PH2O2)2  +  K2CO3  =  2KPH2O2  +  CaCO3. 

The  filtered  solution  is  evaporated  at  a  very  gentle  heat,  stirring 
constantly  from  the  time  it  begins  to  thicken  until  a  dry,  granular 
salt  is  obtained,  which  is  soluble  in  0.6  part  of  cold  and  0.3  part  of 
boiling  water. 

Potassium  iodide,  Potassii  iodidum,  KI  =  165.5  is  made  by  the 
addition  of  iodine  to  a  solution  of  potassium  hydroxide  until  the 
dark -brown  color  no  longer  disappears  : 

6KOH  +  61  =  5KI  +  KIO3  +  3H2O. 

Iodide  and  iodate  of  potassium  are  formed,  and  may  be  separated 
by  crystallization.  A  better  method,  however,  is  to  boil  to  dryness 
the  liquid  containing  both  salts,  and  to  heat  the  mass  after  having 
mixed  it  with  some  charcoal,  in  a  crucible,  when  the  iodate  is  con- 
verted into  iodide  : 

KIO3  +  30  =  KI  +  SCO. 

Experiment  17.  Add  to  a  solution  of  about  3  grammes  of  potassium  hydroxide 
in  about  25  c.c.  of  water  (or  to  the  solution  obtained  by  making  Experiment 
16)  iodine  until  the  brown  color  no  longer  disappears.  (How  much  iodine  will 
be  needed  for  3  grammes  of  KOH  ?)  Evaporate  the  resulting  solution  (What 


140  METALS  AND  THEIR  COMBINATIONS. 

does  this  solution  contain  now  ?)  to  dryness,  mix  the  powdered  mass  with  about 
10  per  cent,  of  powdered  charcoal  and  heat  the  mixture  in  a  crucible  until 
slight  deflagration  has  taken  place.  Dissolve  the  fluid  mass  in  hot  water,  filter 
and  set  aside  for  crystallization;  if  too  much  water  has  been  used  for  dissolving, 
the  liquid  must  be  concentrated  by  evaporation. 

Potassium  iodide  forms  colorless,  cubical  crystals,  which  are  soluble 
in  0.5  part  of  boiling  and  0.8  part  of  cold  water,  also  soluble  in  18 
parts  of  alcohol,  and  2.5  parts  of  glycerin.  When  heated  it  fuses, 
and  at  a  bright-red  heat  is  volatilized  without  decomposition. 

Potassium  bromide,  Potassii  bromidum,  KBr  =  118.8  may  be 
obtained  in  a  manner  analogous  to  that  given  for  potassium  iodide, 
by  the  action  of  bromine  upon  potassium  hydroxide,  etc. 

Or  it  may  be  made  by  the  decomposition  of  a  solution  of  ferrous 
bromide  by  potassium  carbonate  : 

FeBr2  +  K2CO3  =  2KBr  -f  FeCO3. 

Ferrous  carbonate  is  precipitated,  whilst  potassium  bromide  remains 
in  solution,  from  which  it  is  obtained  by  crystallization. 

Potassium  salts  of  interest,  which  have  not  yet  been  mentioned,  will  be  con- 
sidered under  the  head  of  their  respective  acids.  Some  of  these  salts  are 
potassium  chromate  and  permanganate,  and  the  salts  formed  from  organic 
acids,  such  as  potassium  tartrate,  acetate,  etc. 

Analytical  reactions. 
(Potassium  chloride,  KC1,  or  nitrate,  KNO3,  may  be  used.) 

1.  To  a  solution  of  potassium  chloride,  or  to  any  salt  of  potas- 
sium, after  a  few  drops  of  hydrochloric  acid  have  been  mixed  with 
it,  add  platinic  chloride  and  some  alcohol :  a  yellow  crystalline  pre- 
cipitate falls,  which  is  a  double  chloride  of  platinum  and  potassium, 
PtCl4(KCl)2. 

2KC1  +  PtCl4  =  PtCl4(KCl)2; 
2KNO3  +  2HC1  +  Pt014  =  PtCl4(KCl)2  -f  2HNO3. 

The  last  formula  shows  the  necessity  of  adding  hydrochloric  acid, 
which  is  not  required  in  case  potassium  chloride  is  used.  The  ad- 
dition of  alcohol  facilitates  the  precipitation  of  the  double  chloride 
of  potassium  and  platinum,  because  it  is  less  soluble  in  alcohol  than 
in  water. 

2.  To  a  neutral  or  slightly  acid  solution  of  a  potassium  salt  add 
sodium   cobaltic  nitrite :  a  yellow  precipitate  of  potassium  cobaltic 
nitrite,   (KNO2)6.Co2(NO2)6  -f  H2O,  is    produced.     (The  reaction  is 


SODIUM.  141 

not  influenced  by  the  presence  of  alkaline  earths,  earths,  or  metals  of 
the  iron  group.) 

3.  Add  to  a  concentrated  solution  of  a  neutral  potassium  salt  a 
freshly  prepared  strong  solution  of  tartaric  acid :  a  white  precipitate 
of  potassium  acid  tartrate,  KHC4H4O6,  is  slowly  formed.     Addition 
of  alcohol  facilitates  precipitation. 

4.  Potassium  compounds  color  violet  the  flame  of  a  Bunsen  burner 
or  of  alcohol.     The  presence  of  sodium,  which  colors  the  flame  in- 
tensely yellow,  interferes  with  this  test,  as  it  masks  the  violet  caused 
by  potassium.     The  difficulty   may  be  overcome  by  observing  the 
flame  through  a  blue  glass  or  through  a  thin  vessel  filled  with  a  solu- 
tion of  indigo.     The  yellow  light  is  absorbed  by  the  blue  medium, 
while  the  violet  light  passes  through  and  can  be  recognized. 

5.  All  compounds  of  potassium  are  white  (unless  the  acid  has  a 
coloring  effect),  soluble  in  water,  and  not  volatile  at  a  low  red  heat. 


20.  SODIUM  (NATRIUM). 
Nai  =  23. 

Occurrence  in  nature.  Sodium  is  found  very  widely  diffused  in 
small  quantities  through  all  soils.  It  occurs  in  large  quantities  in 
combination  with  chlorine,  as  roc]£=salt,  or  common  salt,  which  forms 
considerable  deposits  in  some  regions,  or  is  dissolved  in  spring  waters, 
and  is  by  them  carried  to  the  rivers,  and  finally  to  the  ocean,  which 
contains  immense  quantities  of  sodium  chloride.  It  is  found,  also, 
as  nitrate,  silicate,  etc. 

Sodium  chloride,  Sodii  chloridum,  NaCl  =  58.4  ( Common 
This  is  the  most  important  of  all  sodium  compounds,  and  also  is  the 
material  from  which  the  other  compounds  are  directly  or  indirectly 

QUESTIONS. — 181.  How  is  potassium  found  in  nature,  and  from  what  sources 
is  the  chief  supply  of  potassium  salts  obtained?  182.  What  color  have  the 
salts  of  the  alkali  metals,  and  which  are  insoluble  ?  183.  Mention  two  pro- 
cesses for  making  potassium  hydroxide,  and  what  are  its  properties?  184. 
Show  by  symbols  the  conversion  of  carbonate  into  bicarbonate  of  potassium. 
185.  Explain  the  principle  of  the  manufacture  of  potassium  nitrate,  and  what 
is  the  office  of  the  latter  in  gunpowder?  186.  How  is  potassium  chlorate  made, 
and  what  are  its  properties  ?  187.  Give  the  processes  for  manufacturing  iodide 
and  bromide  of  potassium,  both  in  words  and  symbols.  188.  State  the  com- 
position .of  potassium  sulphate  and  sulphite.  How  can  they  be  obtained  ? 
189.  What  is  sulphuret  of  potash?  190.  Mention  tests  for  potassium  com- 
pounds. 


142  METALS  AND  THEIR  COMBINATIONS. 

obtained.  Common  table-salt  frequently  contains  small  quantities 
of  calcium  and  magnesium  chlorides,  the  presence  of  which  causes 
absorption  of  moisture,  as  these  compounds  are  hygroscopic,  whilst 
pure  sodium  chloride  is  not. 

In  the  animal  system,  sodium  chloride  is  found  in  all  parts,  it 
being  of  great  importance  in  aiding  the  absorption  of  albuminoid 
substances  and  the  phenomena  of  osmose;  also  by  furnishing, 
through  decomposition,  the  hydrochloric  acid  of  the  gastric  juice. 

Sodium  chloride  is  soluble  in  2.8  parts  of  cold  water,  and  in  2.5 
parts  of  boiling  water  ;  almost  insoluble  in  alcohol  ;  it  crystallizes  in 
cubes  and  has  a  neutral  reaction. 

Sodium  hydroxide,  Sodium  hydrate,  Soda,  NaOH  =  40,  may 
be  obtained  by  the  processes  mentioned  for  potassium  hydroxide, 
which  compound  it  closely  resembles  in  its  chemical  and  most  of  its 
physical  properties. 

Solution  of  soda  is  a  5  per  cent,  solution  of  the  hydroxide  in  water. 

Sodium  carbonate,  Sodii  carbonas,  Na2CO3.10H2O  =  286 
(  Washing  soda,  Sal  sodce).  This  compound  is",  of  "all  alKalme  sub- 
stances, the  one  manufactured  in  the  largest  quantities,  being  used  in 
the  manufacture  of  many  highly  important  articles,  as,  for  instance, 
soap,  glass,  etc. 

Sodium  carbonate  is  made,  according  to  Leblanc's  process,  from 
the  chloride  by  first  converting  it  into  sulphate  (salt-cake)  by  the 
action  of  sulphuric  acid  : 

2NaCl  +  H2SO4  =  2HC1  +  Na2SO, 

The  escaping  vapors  of  hydrochloric  acid  are  absorbed  in  water, 
and  this  liquid  acid  is  used  largely  in  the  manufacture  of  bleaching- 
powder.  The  sodium  sulphate  is  mixed  with  coal  and  limestone 
(calcium  carbonate)  and  the  mixture  heated  in  reverberatory  furnaces, 
when  decomposition  takes  place,  calcium  sulphide,  sodium  carbonate, 
and  carbonic  oxide  being  formed  : 

Na2SO4  +  40  +  CaCO3  =  CaS  +  Na-jCOg  +  4CO 


The  resulting  mass,  known  as  black-ash,  is  washed  with  water, 
which  dissolves  the  sodium  carbonate,  whilst  calcium  sulphide  enters 
into  combination  with  calcium  oxide,  thus  forming  an  insoluble 
double  compound  of  oxy-sulphide  of  calcium. 

The  liquid  obtained  by  washing  the  black  -ash,  when  evaporated 
to  dryness,  yields  crude  sodium  carbonate,  or  "  soda  ash  -"  when  this 


SODIUM.  143 

is  dissolved  and  crystallized  it  takes  up  ten  molecules  of  water, 
forming  the  ordinary  washing  soda. 

Sodium  carbonate  is  manufactured  also  by  the  so-called  ammonia 
process,  or  the  Solvay  process.     This  depends  on  the  decomposition 
of  sodium  chloride  by  ammonium  bicarbonate  under  pressure,  when 
sodium  bicarbonate  and  ammonium  chloride  are  formed,  thus : 
NaCl  +  NH4HCO3  =  NH.C1  +  NaHCO3. 

The  sodium  acid  carbonate  thus  obtained  is  converted  into  carbo- 
nate by  heating : 

2NaHCO3  =  Na2CO3  +  H2O  +  CO2. 

The  carbon  dioxide  obtained  by  this  action  is  caused  to  act  upon 
ammonia,  liberated  from  the  ammonium  chloride,  obtained  as  one  of 
the  products  in  the  first  reaction.  Ammonium  carbonate  is  thus 
regenerated  and  used  in  a  subsequent  operation  for  the  decomposition 
of  common  salt. 

Sodium  carbonate  has  strong  alkaline  properties ;  it  is  soluble  in 
1.6  parts  of  cold  water,  and  in  much  less  water  at  higher  temper- 
atures ;  the  crystals  lose  water  on  exposure  to  the  air,  falling  into  a 
white  powder;  heat  facilitates  the  expulsion  of  the  water  of  crys- 
tallization, and  is  applied  in  making  the  dried  sodium  carbonate, 
Sodii  carbonas  exsiccatJis  of  the  U.  S.  P.,  which  should  contain  about 
73  per  cent,  of  anhydrous  sodium  carbonate. 

Sodium  bicarbonate,  Sodii  bicarbonas,  NaHCO3=84.  Ob- 
tained, as  stated  in  the  previous  paragraph,  by  the  ammonia- soda 
process.  It  can  also  be  made  by  passing  carbon  dioxide  over  sodium 
carbonate  from  which  the  larger  portion  of  water  of  crystallization 
has  been  expelled : 

NajCOa  +  H2O  +  CO2  =  2NaHCO3. 

It  is  a  white  powder,  having  a  cooling,  mildly  saline  taste,  and  a 
slightly  alkaline  reaction.  Soluble  in  11.3  parts  of  cold  water,  and 
insoluble  in  alcohol.  It  is  decomposed  by  heat  or  by  hot  water  into 
sodium  carbonate,  water,  and  carbon  dioxide. 

Sodium  sulphate,  Sodii  sulphas,  Na2SO410H2O  =  322  (Glaubers 
salt).  Made,  as  mentioned  above,  by  the  action  of  sulphuric  acid  on 
sodium  chloride,  dissolving  the  salt  thus  obtained  in  water,  and  crys- 
tallizing. Large,  colorless,  transparent  crystals,  rapidly  efflorescing 
on  exposure  to  air.  Soluble  in  2.8  parts  of  water  at  15°  C.  (59°  F.), 
in  0.25  part  at  34°  C.  (93°  F.),  and  in  0.47  part  of  boiling  water. 


144  METALS  AND  THEIR  COMBINATIONS. 

Experiment  18.  Dissolve  about  10  grammes  of  crystallized  sodium  carbonate 
in  10  c.c.  of  hot  water,  add  to  this  solution  dilute  sulphuric  acid  until  all  effer- 
vescence ceases  and  the  reaction  on  litmus-paper  is  exactly  neutral.  Evaporate 
to  about  20  c.c.,  and  set  aside  for  crystallization.  Explain  the  action  taking 
place,  and  state  how  much  H2S04,  and  how  much  of  the  diluted  sulphuric 
acid,  U.  S.  P.,  are  needed  for  the  decomposition  of  10  grammes  of  crystallized 
sodium  carbonate. 

Sodium  sulphite,  Sodii  sulphis,  Na2SO3.7H2O  =  252.  Sodium 
bisulphite,  Sodii  bisulphis,  NaHSO3  =  1O4.  By  saturating  a  cold 
solution  of  sodium  carbonate  with  sulphur  dioxide,  sodium  bisulphite 
is  formed,  and  separates  in  opaque  crystals : 

Na^COg  -f  2SO2  +  H2O  =  2NaHSO3  +  CO2. 

If  to  the  sodium  bisulphite  thus  obtained  a  quantity  of  sodium  car- 
bonate be  added,  equal  to  that  first  employed,  the  normal  salt  is  formed : 
2NaHS03  +  Na^COs  =  2^803  +  H2O  -f  CO2 

Sodium  thlosulphate,  Sodium  hyposulphite,  Sodii  hyposul- 
phis,  Na2S2O3.5H2O— 248.  made  by  digesting  a  solution  of  sodium 
sulphite  with  powdered  sulphur,  when  combination  slowly  takes  place  : 
Na,S03  +  S  =  Na&O,. 

It  is  used  under  the  name  of  "hypo"  in  photography  to  dissolve 
Chloride,  bromide,  or  iodide  of  silver. 

Disodium  hydrogen  phosphate,  Sodii  phosphas,  Na2HPO4. 
12H2O  =  358  (Sodium  phosphate)  is  made  from  calcium  phosphate  by 
the  action  of  sulphuric  acid,  which  removes  two-thirds  of  the  calcium, 
forming  calcium  sulphate,  while  acid  phosphate  of  calcium  is  formed 
and  remains  in  solution  : 

Ca3(POJ2  +  2H2S04  =  2CaS04  +  CaH4(PO4)2. 

The  solution  is  filtered  and  sodium  carbonate  added,  when  calcium 
phosphate  is  precipitated,  phosphate  of  sodium,  carbon  dioxide,  and 
water  being  formed  : 

CaH4(P04)2  +  Na^COg  ==  CaHPO4  +  H2O  +  CO2  +  Na2HPO4. 

The  filtered  and  evaporated  solution  yields  crystals  of  sodium 
phosphate,  which  have  a  slightly  alkaline  reaction  to  litmus,  but  not 
to  phenol-phtalein. 

Experiment  19.  Mix  thoroughly  30  grammes  of  bone-ash  with  10  c.c.  of 
sulphuric  acid,  let  stand  for  some  hours,  add  20  c.c.  of  water,  and  again  set 
aside  for  some  hours.  Mix  with  40  c.c.  of  water,  heat  to  the  boiling-point,  and 
filter.  The  residue  on  the  filter  is  chiefly  calcium  sulphate.  To  the  hot  filtrate 
of  calcium  acid  phosphate  add  concentrated  solution  of  sodium  carbonate  until 
a  precipitate  ceases  to  form  and  the  liquid  is  faintly  alkaline,  filter,  evaporate, 
and  let  crystallize. 


SODIUM.  145 

When  sodium  phosphate  is  heated  to  a  low  red  heat  it  loses  water, 
and  is  converted  into  pyrophosphate,  which,  dissolved  in  hot  water, 
and  crystallized,  forms  the  sodium  pyrophosphate,  Na4P2O7.10H2O  of 
the  U.  S.  P. 

The  normal  sodium  phosphate,  Na3PO4,  is  known  also,  but  it  is  not  a  very 
stable  compound,  being  acted  upon  even  by  the  moisture  and  carbon  dioxide 
of  the  air,  with  the  formation  of  sodium  carbonate  and  disodium  hydrogen 
phosphate,  thus : 

2Na3PO4  +  H2O  +  CO2  =  2Na2HPO4  +  Na,CO3. 

Sodium  nitrate,  Sodii  nitras,  NaNO3=  85  (Chili  saltpetre,  Cubic 
nitre).  Found  in  nature,  and  is  purified  by  crystallization.  The 
crystals  are  transparent,  deliquescent,  and  readily  soluble. 

Sodium  nitrite,  NaNO2,  is  formed  by  heating  the  nitrate  to  a  sufficiently  high 
temperature  to  expel  one-third  of  the  oxygen ;  or,  better,  by  treating  the  fused 
nitrate  with  metallic  lead,  which  latter  is  converted  into  oxide.  The  sodium 
nitrite  which  is  formed  is  dissolved  and  purified  by  crystallization. 

Sodium  borate,  Sodii  boras,  Na2B4O7  -f  10H2O  =  382.2  (Borax^ 
This  salt  occ'Ury  tcr "Clear  Lake,  Nevada,  and  in  several  lakes  in  Asia. 
It  is  manufactured  by  adding  sodium  carbonate  to  the  boric  acid 
found  in  Tuscany,  Italy.  It  forms  colorless,  transparent  crystals, 
but  is  sold  mostly  in  the  form  of  a  white  powder.  It  is  slightly 
efflorescent,  is  soluble  in  16  parts  of  cold,  and  in  0.5  part  of  boiling 
water ;  insoluble  in  alcohol,  but  soluble  in  one  part  of  glycerin  at 
80°  C.  (176°  F.).  When  heated,  borax  puffs  up,  loses  water  of 
crystallization,  and  at  red  heat  it  melts,  forming  a  colorless  liquid 
which,  on  cooling,  solidifies  to  a  transparent  mass,  known  as  fused 
borax,  or  borax  glass.  Molten  borax  has  the  power  to  combine  with 
metallic  oxides,  forming  double  borates,  some  of  which  have  a  char- 
acteristic color,  for  which  reason  borax  is  used  in  blow-pipe  analysis. 
Borax  has  antiseptic  properties,  preventing  the  decomposition  of  some 
organic  substances. 

Other  sodium  salts  which  are  official  are  sodium  hypophosphite, 
NaPH2O2-{-H2O;  bromide,  NaBr;  iodide,  Nal;  chlorate,  NaClOa. 
These  salts  may  be  obtained  by  processes  analogous  to  those  given 
for  the  corresponding  potassium  compounds. 

Tests  for  sodium. 
(Sodium  chloride,  NaCl,  may  be  used.) 

1.  As  all  salts  of  sodium  are  soluble  in  water,  we  cannot  precipi- 
tate this  metal  in  the  form  of  a  compound  by  any  of  the  common 

10 


146  METALS  AND  THEIR  COMBINATIONS. 

reagents.     (Potassium  antimoniate  precipitates  neutral   solution  of 
sodium  salts,  but  this  test  is  not  reliable.) 

2.  The  chief  reaction  for  sodium  is  the  flame-test,  compounds  of 
sodium  imparting  to  a  colorless  flame  yellow  color,  which  is  very 
intense,  brilliant,  and  luminous.     A  crystal  of  potassium  dichromate 
appears  colorless,  and  a  paper  coated  with  red  mercuric  iodide  appears 
white,  when  illuminated  by  the  yellow  sodium  flame.     (The  spectro- 
scope shows  a  characteristic  yellow  line.) 

3.  Sodium  compounds  are  white  and  are  not  volatile  at  or  below  a 
red  heat. 

Lithium,  Li  =  7.  Found  in  nature  in  combination  with  silicic  acid  in  a  few 
rare  minerals  or  as  a  chloride  in  some  spring  waters.  Of  inorganic  salts, 
lilhium  bromide  and  carbonate  are  official.  Hydroxide,  carbonate,  and  phosphate 
of  lithium  are  much  less  soluble  than  the  corresponding  compounds  of  potas- 
sium and  sodium.  Sodium  phosphate  added  to  a  strong  solution  of  a  lithium 
salt  produces,  on  boiling,  a  white  precipitate  of  lithium  phosphate,  Li3PO4. 
Lithium  compounds  color  the  flame  a  beautiful  crimson  or  carmine-red. 


f\  1    U 
* 


21.  AMMONIUM. 
NH4i  =  18. 

General  remarks.  The  salts  of  ammonium  show  so  much  resem- 
blance, both  in  their  physical  and  chemical  properties,  to  those  of  the 
alkali-metals,  that  they  may  be  studied  most  conveniently  at  this 
place. 

The  compound  radical  NH4  acts  in  these  ammonium  salts  very 
much  like  one  atom  of  an  alkali-metal,  and,  therefore,  frequently  has 
been  looked  upon  as  a  compound  metal.  The  physical  metallic  prop- 
erties (lustre,  etc.)  of  ammonium  cannot  be  fully  demonstrated,  as  it 
is  not  capable  of  existing  in  a  separate  or  free  state.  There  is  known, 
however,  an  alloy  of  ammonium  and  mercury,  which  may  be  obtained 

QUESTIONS.  —  191.  What  is  the  composition  of  common  salt;  how  is  it  found 
in  nature,  and  what  is  it  used  for?  192.  Describe  Leblanc's  and  the  Solvay 
process  for  manufacturing  soaium  carbonate  on  a  large  scale.  193.  How  much 
water  is  in  100  pounds  of  the  crystallized  sodium  carbonate?  194.  What  is 
Glauber  salt,  and  how  is  it  made?  195.  State  the  composition  of  disodium 
hydrogen  phosphate,  and  how  is  it  prepared  from  calcium  phosphate?  196. 
What  difference  exists  between  sodium  carbonate  and  bicarbonate  both  in 
regard  to  physical  and  chemical  properties?  197.  Give  the  composition  of 
sodium  hyposulphite;  what  is  it  used  for?  198.  Which  sodium  salts  are 
soluble,  and  which  are  insoluble?  199.  How  does  sodium  and  how  does 
lithium  color  the  flame?  200.  Which  lithium  salts  are  official? 


AMMONIUM.  147 

by  dissolving  potassium  in  mercury,  and  adding  to  the  potassium- 
amalgam  thus  formed,  a  strong  solution  of  ammonium  chloride,  when 
potassium  chloride  and  ammonium-amalgam  are  formed.  The  latter 
is  a  soft,  spongy,  metallic-looking  substance,  which  readily  decomposes 
into  mercury,  ammonia,  and  hydrogen  : 

HgK  +  NH4C1  =  KC1  +  NH4Hg; 
NH4Hg  =  NH3  +  H  +  Hg. 

The  source  of  all  ammonium  compounds  is  ammonia  NH3,  or  am- 
monium hydroxide,  NH4OH,  both  of  which  have  been  considered 
heretofore. 

Ammonium  chloride,  Ammonii  chloridum,  NH4C1  =  53.4  (Sal-_ 
ammoniac).  Obtained  by  saturating  the  "ammoniacal  liquor77  of  the 
gas-works  with  hydrochloric  acid,  evaporating  to  dryness,  and  puri- 
fying the  crude  article  by  sublimation. 

Pure  ammonium  chloride  either  is  a  white,  crystalline  powder,  or 
occurs  in  the  form  of  long,  fibrous  crystals,  which  are  tough  and 
flexible ;  it  has  a  cooling,  saline  taste ;  is  soluble  in  3  parts  of  cold, 
and  in  1  part  of  boiling  water;  and  like  all  ammonium  compounds, 
is  completely  volatilized  by  heat. 

Experiment  20.  To  10  c.c.  of  water  of  ammonia  add  hydrochloric  acid  until 
the  solution  is  neutral  to  test  paper.  Evaporate  to  dryness  and  use  the  salt 
for  the  analytical  reactions  mentioned  below.  How  many  c.c.  of  32  per  cent, 
hydrochloric  acid  are  required  to  saturate  10  c.c.  of  10  per  cent,  ammonia 
water  ? 

Ammonium  carbonate,  Ammonii  carbonas,  NH4HCO3.NH4 
NH2CO2=157.  Commercial  ammonium  carbonate  is  not  the  normal 
salt,  but,  as  shown  by  the  above  formula,  a  combination  of  acid 
ammonium  carbonate  with  ammonium  carbamate.  It  is  obtained  by 
sublimation  of  a  mixture  of  ammonium  chloride  and  calcium  car- 
bonate, when  calcium  chloride  is  formed,  ammonia  gas  and  water 
escape,  and  ammonium  carbonate  condenses  in  the  cooler  part  of  the 
apparatus  : 

2CaCO3  +  4NH4C1  =  NH4HCO3  NH4NH2CO2  +  2CaCl2  +  H2O  +  NH3. 

Ammonium  carbonate  thus  obtained  forms  white,  translucent  masses,  losing 
both  ammonia  and  carbon  dioxide  on  exposure  to  the  air,  becoming  opaque, 
and  finally  converted  into  a  white  powder  of  acid  ammonium  carbonate. 

NH4HCO3  NH4NH2CO2  =  NH4HgO3  +  2NH3  +  CO2. 

When  commercial  ammonium  carbonate  is  dissolved  in  water  the  carbamate 
unites  with  one  molecule  of  water,  forming  normal  ammonium  carbonate. 

NH4NH2CO2  +  H2O  =  (NH4)2CO3. 


148  METALS  AND  THEIR  COMBINATIONS. 

A  solution  of  the  common  ammonium  carbonate  in  water  is,  consequently,  a 
liquid  containing  both  acid  and  normal  carbonate  of  ammonium  ;  by  the  addi- 
tion of  some  ammonia  water  the  acid  carbonate  is  converted  into  the  normal 
salt.  The  solution  thus  obtained  is  used  frequently  as  a  reagent. 

The  Aromatic  spirit  of  ammonia  (sal  volatile)  is  a  solution  of  normal  ammo- 
nium carbonate  in  diluted  alcohol  to  which  some  essential  oils  have  been  added. 

Ammonium  sulphate,  (NH4)2SO4,  Ammonium  nitrate,  NH4N03, 
and  Ammonium  phosphate,  (NH4)2HPO4,  may  be  obtained  by  the 
addition  of  the  respective  acids  to  ammonia  water  or  ammonium 
carbonate  : 

H2SO4  +  2NH4OH  =  (NHJ2S04  +  2H2O. 
HNO8  +  NH4OH  =  NH4N03  -f  H2O. 
H3PO4  +  2NH4OH  =  (NH4)2HPO4  4-  2H2O. 
H2S04  -f-  (NH4)2C03  =  (NH4)2S04  +  H2O  +  CO2. 

Ammonium  iodide,  Ammonii  iodidum,  NH4I,  and  Ammonium 
bromide,  Ammonii  bromidum,  NH4Br,  may  be  obtained  by  mixing 
together  strong  solutions  of  potassium  iodide  (or  bromide)  and  am- 
monium sulphate,  and  adding  alcohol,  which  precipitates  the  potas- 
sium sulphate  formed  ;  by  evaporation  of  the  solution  the  ammonium 
iodide  (or  bromide)  is  obtained  : 

2KI     +  (NH4)2SO4  =  2NH4I     +  K2SO4; 
2KBr  +  (NH4)2S04  =  2NH,Br  +  K2SO4. 


Another  mode  of  preparing  these  compounds  is  by  the  decomposi- 
tion of  ferrous  bromide  (or  iodide)  by  ammonium  hydroxide  : 
FeBr2  +  2NH4OH  =  2NH4Br  +  Fe(OH)2. 

Ammonium  iodide  is  the  principal  constituent  of  the  Decolorized 
tincture  of  iodine. 

Ammonium   hydrogen   sulphide,  NH4SH  (Ammonium  hydro- 
sulphide  j  Ammonium  sulphydrate).     Obtained  by  passing  hydrogen 
sulphide  through  water  of  ammonia  until  this  is  saturated  : 
H2S  +  NH4OH  ==  NH4SH  4-  H2O. 

The  solution  thus  obtained  is,  when  recently  prepared,  a  colorless 
liquid,  having  the  odor  of  both  ammonia  and  of  hydrogen  sulphide  ; 
when  exposed  to  the  air  it  soon  assumes  a  yellow  color.  By  the 
addition  of  ammonia  water  it  is  converted  into  ammonium  sulphide, 

(NH4)2S: 

NH.SH  +  NH4OH  =  (NH4)2S  +  H2O. 

Both  substances,  the  ammonium  hydrogen  sulphide  and  ammonium  sulphide, 
are  valuable  reagents,  frequently  used  for  precipitation  of  certain  heavy  metals, 
or  for  dissolving  certain  metallic  sulphides. 


AMMONIUM. 


149 


Analytical  reactions. 
(Ammonium  chloride,  NH4C1,  may  be  used.) 

1.  All  compounds  of  ammonium  are  volatilized  by  heating  to  a  low 
red  heat. 

2.  All  compounds  of  ammonium  evolve  ammonia  gas  when  heated 
with  hydroxide  of  calcium,  potassium,  or  sodium.    The  ammonia  may 
be  recognized  by  its  odor,  or  by  its  action  on  paper  moistened  with 
solution  of  cupric  sulphate,  which  is  thereby  colored  dark-blue,  or  by 
causing  the  appearance  of  dense  white  fumes  of  ammonium  chloride, 
upon  holding  a  glass  rod,  moistened  with  hydrochloric  acid,  in  the 
gas. 

3.  Add  to  solution  of  ammonium  salt  some  platinic  chloride,  a  few 
drops  of  hydrochloric  acid,  and  some  alcohol ;  a  yellow  precipitate 
of  ammonium  platinic  chloride,  (NH4Cl)2PtCl4,  is  produced.     See 
explanation  of  the  corresponding  potassium  reaction  on  page  140. 

4.  The  addition  of  sodium  cobaltic  nitrite  causes  in  neutral  or 
acid  solutions  a  yellow  precipitate  of  ammonium  cobaltic  nitrite, 
(NH1N02)6.Co2.(N02)6. 

5.  Ammonium  salts  are  colorless,  and  (almost  all)  soluble  in  water. 
Traces  of  ammonium  compounds  may  be  detected  by  alkaline  mer- 
curic-potassium iodide  (Nessler's  solution),  which  causes  a  reddish- 
brown  precipitate  or  coloration. 

Summary  of  analytical  characters  of  the  alkali-metals. 


Potassium. 

Sodium. 

Lithium. 

Ammonium. 

Sodium  cobaltic  nitrite  . 

Yellow  pre- 

Yellow pre- 

Platinic chloride  •     .     .     . 

cipitate. 
Yellow  pre- 

cipitate. 
Yellow  pre- 

Sodium bitartrate 

cipitate. 
White  preci- 

cipitate. 
White  preci- 

Sodium  phosphate              . 

pitate. 

^Vhite  preci- 

pitate. 

Sodium  hydroxide 

pitate  in  cone, 
solution  on 
boiling. 

Ammonia 

Action  of  heat      .... 
Flame  color 

Fusible. 
Violet 

Fusible. 
Yellow 

Fusible. 
Crimson 

gas. 
Volatile. 

QUESTIONS. — 201.  What  is  ammonium,  and  why  is  it  classed  with  the  alkali- 
metals?  202.  Is  ammonium  known  in  a  separate  state?  203.  What  is  ammo- 
nium-amalgam, how  is  it  obtained,  and  what  are  its  properties  ?  204  What  is 


150  METALS  AND  THEIE  COMBINATIONS. 

22.  MAGNESIUM. 
Mgii  =  24.3. 

General  remarks.  Magnesium  occupies  a  position  intermediate 
between  the  alkali  metals  and  the  alkaline  earths.  To  some  extent 
it  resembles  also  the  heavy  metal  zinc,  with  which  it  has  in  common 
the  volatility  of  the  chloride,  the  solubility  of  the  sulphate,  and  the 
isomorphism  of  several  of  its  compounds  with  the  analogously  con- 
stituted compounds  of  zinc. 

Occurrence  in  nature.  Magnesium  is  widely  diffused  in  nature, 
and  several  of  its  compounds  are  found  in  large  quantities.  It  occurs 
as  chloride  and  sulphate  in  many  spring  waters  and  in  the  salt-mines 
01  Strassfurt;  as  carbonate  in  th,e  ^ineralmaqnefdte  .•  as  double  car- 
bonate of  magnesium  and  calcium  in  the  mmeraTHo/omife  (magnesian 
limestone),  which  forms  entire  mountains ;  as  silicate  of  magnesium 
in  the  minerals  serpentine,  meerschaum,  talc,  asbestos,  soapstone,  etc. 

Metallic  magnesium  may  be  obtained  by  the  decomposition  of 
magnesium  cHprideby  sodium : 

MgCl2  +  2Na  =  2NaCl  +  Mg. 

Magnesium  is  an  almost  silver- white  metal,  losing  its  lustre  rapidly 
in  moist_air-Jb^LO^dajdoji_Qf_the  surface.  It  decomposes^IroT^water 
with  liberation  of  hydrogen : 

Mg  +  2H2O  =  2H  +  Mg(OH)2. 

When  heated  to  a  red  heat  it  burns  with  a  brilliant  bluish-white 
light  forming  magnesium  oxide. 

Magnesium  carbonate,  Magnesii  carbonas.  Approximately  : 
(Mg-CO3)4.Mg(OH)2.5H2O  (Magnesia  alba,  Light  magnesia).  The 
normal  magnesium  carbonate,  MgCO3,  is  found  in  nature,  but  the 
official  preparation  contains  carbonate,  hydroxide,  and  water.  It  is 
obtained  by  boiling  a  solution  of  magnesium  sulphate  with  solution 

the  source  of  ammonium  compounds  ?  205.  State  the  composition,  mode  of 
preparation,  and  properties  of  sal-ammoniac.  206.  How  is  ammonium  car- 
bonate manufactured,  and  what  difference  exists  between  the  solid  article  and 
its  solution?  207.  State  the  composition  of  ammonium  sulphide  and  of  am- 
monium hydrogen  sulphide ;  how  are  they  made,  and  what  are  they  used  for  ? 
208.  By  what  process  may  ammonium  sulphate,  nitrate,  and  phosphate  be 
obtained  from  ammonium  hydroxide  or  ammonium  carbonate,  and  what  chemi- 
cal change  takes  place?  209.  How  does  heat  act  upon  ammonium  compounds? 
210.  Give  analytical  reactions  for  ammonium  salts. 


MAGNESIUM.  151 

of  sodium  carbonate,  when  the  carbonate  is  precipitated,  some  carbon 
dioxide  evolved,  and  sodium  sulphate  remains  in  solution  : 

5MgSO4  +  5Na,CO3  +  6H2O  =  (MgCO3)4  Mg(OH)2.5H2O  -f  5Na2SO4  +  CO2. 

By  filtering,  washing,  and  drying  the  precipitate,  it  is  obtained  in 
the  form  of  a  white,  light  powder  ;  if,  however,  the  above-mentioned 
solutions  are  mixed,  evaporated  to  dryness,  and  the  sodium  sulphate 
removed  by  washing,  the  magnesium  carbonate  is  left  in  a  more  dense 
condition,  and  is  then  known  as  heavy  magnesium  carbonate. 

Experiment  21.  Dissolve  10  grammes  of  magnesium  sulphate  in  hot  water 
and  add  a  concentrated  solution  of  sodium  carbonate  until  no  more  precipitate 
is  formed.  Collect  the  precipitated  magnesium  carbonate  on  a  filter  and  dry  it 
at  a  low  temperature.  (How  much  crystallized  sodium  carbonate  is  needed 
for  the  decomposition  of  10  grammes  of  crystallized  magnesium  sulphate?) 
Notice  that  the  dried  precipitate  evolves  carbon  dioxide  when  heated  with 
acids. 


Magnesium  oxide,  Magnesia,  MgO  =  40.3  (  Calcined  magnesia, 
ia)  ,  is  obtained  by  heating  light  magnesium  carbonate 
in  a  crucible  to  a  full  red  heat,  when  all  carbon  dioxide  and  water 
are  expelled  : 

(MgCO3)4.Mg(OH)2.5H20  =  5MgO  +  4CO2  +  6H2O. 

It  is  a  very  light,  amorphous,  white,  almost  tasteless  powder,  which 
absorbs  moisture  and  carbon  dioxide  gradually  from  the  air;  in  con- 
tact with  water  it  forms  the  hydroxide  Mg(OH)2,  which  is  almost 
insoluble  in  water,  requiring  of  the  latter  over  50,000  parts  for  solu- 
tion. Milk  of  magnesia  is  the  hydroxide  suspended  in  water  (1  part 
in  about  15). 

The  heavy  magnesia,  magnesia  ponderosa  of  the  U.  S.  P.,  differs 
from  the  common  or  light  magnesia,  not  in  its  chemical  composition, 
but  merely  in  its  physical  condition,  being  a  white  ?  rlpngg  powder 
obtained  by  heating  the  heavy  magnesium  carbonate. 

Experiment  22.  Place  1  gramme  of  magnesium  carbonate,  obtained  in  per- 
forming Experiment  21,  into  a  weighed  crucible  and  heat  to  redness,  or  until 
by  further  heating  no  more  loss  in  weight  ensues.  Treat  the  residue  with 
dilute  hydrochloric  acid  and  notice  that  no  evolution  of  carbon  dioxide  takes 
place.  What  is  the  calculated  loss  in  weight  of  magnesium  carbonate  when 
converted  into  oxide,  and  how  does  this  correspond  with  the  actual  loss  deter- 
mined by  the  experiment  ? 

),  Magnesii  sulphas,  Mg-SO4.7H2O  =  246.3 
from  spring  waters,   from   the  mineral 


152  METALS  AND  THEIR  COMBINATIONS. 

Kieserite,  MgSo4.H2O,  and  by  decomposition  of  the  native  carbonate 
by  sulphuric  acid : 

MgCO3  +  H2SO4  =  MgSO4  +  CO2  +  H2O. 

It  forms  colorless  crystals,  which  have  a  cooling,  saline,  and  bitter 
taste,  a  neutral  reaction,  and  are  easily  soluble  in  water. 

Analytical  reactions. 

(Magnesium  sulphate,  MgSO4,  may  be  used.) 

1.  Add  to  a  magnesium  solution  potassium  or  sodium  carbonate 
and  heat :  a  white  precipitate  of  basic  magnesium  carbonate,  4MgCO3. 
Mg(OH)2,  is  produced. 

2.  Add  to  a  magnesium  solution  ammonium  carbonate  (or  ammo- 
nium hydroxide) :   part  of  the  magnesium  will  be  precipitated  as 
carbonate  (or  hydroxide).     These  precipitates,  however,  are  soluble 
in  ammonium  chloride  and  many  other  ammonium  salts:  if  these 
latter  had  been  added  previously  to  the  magnesium  solution,  ammo- 
nium carbonate  (or  hydroxide)  would  cause  no  precipitation.     (The 
dissolving  action  of  the  ammonium  chloride  is  due  to  the  tendency 
of  magnesium  to  form  double  salts  with  ammonium  salts.) 

3.  To  solution  of  magnesium  add  a  solution  containing  sodium 
phosphate,  ammonium  chloride,  and  ammonia:  a  white  crystalline 
precipitate  of  magnesium  ammonium  phosphate,  MgNH4PO4,  is  pro- 
duced, which  is  somewhat  soluble  in  water,  but  almost  insoluble  in 
water  containing  some  ammonia. 

4.  Salts  of  magnesium  are  wrhite  and  soluble,  except  the  carbonate, 
phosphate,  and  arsenate;  the  oxide  and  hydroxide  also  are  insoluble; 
the  latter  is  precipitated  "by  sodium  or  potassium  hydroxide. 

'23.    CALCIUM. 
Caii  =  40  (39.91). 

General  remarks  regarding-  the  metals  of  the  alkaline  earths. 
The  three  metals,  calcium,  barium,  and  strontium,  form  the  second 

QUESTIONS. — 211.  How  is  magnesium  found  in  nature  ?  212.  By  what  pro- 
cess is  metallic  magnesium  obtained?  213.  Give  the  physical  and  chemical 
properties  of  magnesium.  214.  State  two  methods  by  which  magnesium  oxide 
can  be  obtained.  215.  What  is  calcined  magnesia?  216.  State  the  composi- 
tion and  properties  of  the  official  magnesium  carbonate,  and  how  it  is  made. 
217.  What  is  Epsom  salt,  and  how  is  it  obtained  ?  218.  Which  compounds  of 
magnesium  are  insoluble?  219.'  Give  tests  for  magnesium  compounds.  220. 
How  can  the  presence  of  magnesium  be  demonstrated  in  a  mixture  of  mag- 
nesium sulphate  and  sodium  sulphate  ? 


CALCIUM.  153 

group  of  light  metals.  Similar  to  the  alkali-metals,  they  decompose 
water  at  the  ordinary  temperature  with  liberation  of  hydrogen;  their 
separation  in  the  elementary  state  is  even  more  difficult  than  that  of 
the  alkali-metals. 

They  differ  from  the  latter  by  forming  insoluble  carbonates  and 
phosphates  (those  of  the  alkalies  are  soluble),  from  the  earths  by 
their  soluble  hydroxides  (those  of  the  earths  are  insoluble),  and  from 
all  heavy  metals  by  the  solubility  of  their  sulphides  (those  of  heavy 
metals  are  insoluble).  The  sulphates  are  either  insoluble  (barium) 
or  sparingly  soluble  (strontium  and  calcium).  The  hydroxides  and 
carbonates  are  decomposed  by  heat,  water  or  carbon  dioxide  being 
expelled  and  the  oxides  formed.  In  case  of  calcium  carbonate  this 
decomposition  takes  place  easily,  while  the  carbonates  of  barium 
and  strontium  require  a  much  higher  temperature.  They  are  bivalent 
elements. 

Occurrence  in  nature.  Calcium  is  one  of  the  most  abundantly 
occurring  elements.  As  carbonate  (CaCO3)  it  is  found  in  the  form 
of  ^ale-spar,  limestone^  chalk,  marble,  shells  of  gggg_an(^  mollusca, 
etc.,  or,  as  acid  carbonate,  dissolved  in  water.  The  sulphate  is  found 
as  gypsum  or  alabaster,  CaSO42H2O;  the  phosphate,  Ca3(PO4)2,  in 
the  different  phosphatic  rocks  (apatite,  etc.) ;  the  fluoride,  CaF2,  as 
fluor-spar;  the  chloride,  CaCl2,  in  some  waters,  and  the  silicate  in 
many  rocks.  It  enters  the  vegetable  and  animal  system  in  various 
forms  of  combination,  chiefly,  however,  as  phosphate  and  sulphate. 

Calcium^pxide,  Lime,  Calx,  CaO  =  56  ( Quick-lime,  Burned 
lime),  is  obtained  on  a  large  scale  by  the  common  process  of  lime- 
burning,  wfyoJa4g  the  Beating  pf  limestone  or  any  other  calcium  car- 
bonate to  about  800°  C.  (1472°  F.),  in  furnaces  termed  lime-kilns. 
On  a  small  scale  decomposition  may  be  accomplished  in  a  suitable 
crucible  over  a  blowpipe  flame : 

CaCO3  =  CaO  +  CO2. 

The  pieces  of  oxide  thus  formed  retain  the  shape  and  size  of  the 
carbonate  used  for  decomposition. 

Lime  is  a  white,  odorless,  amorphous,  infusible  substance,  of  alka- 
line taste  and  reaction;  exposed  to  the  air  it  gradually  absorbs 
moisture  and  carbon  dioxide,  the  mixture  thus  formed  being^known 
as  air- slaked  lime. 

Lime  occupies  among  bases  a  position  similar  to  that  of  sulphuric 


154  METALS  AND  THEIE  COMBINATIONS. 

acid  among  acids,  and  is  used  directly  or  indirectly  in  many  branches 
of  chemical  manufacture. 

Calcium  hydroxide,  Calcium  hydrate,  Ca(OH)2  (Slaked  lime). 
When  water  is1  Bphukled  upon  pieces  of  calcium  oxide,  theTWoHSub- 
stances  combine  chemically,  liberating  much  heat;  the  pieces  swell 
up,  and  are  converted  gradually  into  a  dry,  white  powder,  which  is 
the  slaked  lime.  When  this  is  mixed  with  water,  the  so-called  milk 
of  lime  is  formed 

Lime-water,  Liquor  calcis  (Solution  of  lime).  This  is  a  sat- 
urated solution  of  calcium  hydroxide  in  water :  10,000  parts  of  the 
latter  dissolving  about  15  to  17  parts  of  hydroxide.  In  making 
lime-water,  1  part  of  calcium  oxide  is  slaked  and  agitated  occasionally 
during  half  an  hour  with  30  parts  of  water.  The  mixture  is  then 
allowed  to  settle,  and  the  liquid,  containing  besides  calcium  hydroxide 
the  salts  of  the  alkali-metals  which  may  have  been  present  in  the 
lime,  is  decanted  and  thrown  away.  To  the  calcium  hydroxide  left, 
and  thus  purified,  300  parts  of  water  are  added  and  occasionally 
shaken  in  a  well-stoppered  bottle,  from  which  the  clear  liquid  may 
be  poured  off  for  use. 

Lime-water  is  a  colorless,  odorless  liquid,  having  a  feebly  caustic 
taste  and  an  alkaline  reaction.  When  heated  to  boiling  it  becomes 
turbid  by  precipitation  of  calcium  hydroxide  (or  perhaps  oxide)  which 
re-dissolves  when  the  liquid  is  cooled.  Carbon  dioxide  causes  a  pre- 
cipitation of  calcium  carbonate. 

Experiment  23.    Make  lime-water  according  to  directions  given  above. 

Calcium  carbonate,  Calcii  carbonas  praecipitatus,  CaCO3  = 
1OO.  Precipitated  calcium  carbonate  is  obtained  as  a  white,  taste- 
less, neutral,  impalpuble  powder  by  mixing  solutions  of  calcium 
chloride  and  sodium  carbonate  : 

CaCl2  +  Na2CO3  ==  2NaCl  +  CaCO3. 

Experiment  24.  Add  to  about  10  grammes  of  marble  (calcium  carbonate)  in 
small  pieces,  hydrochloric  acid  as  long  as  effervescence  takes  place  ;  filter  the 
solution  of  calcium  chloride  thus  obtained  and  add  to  it  solution  of  sodium 
carbonate  as  long  as  a  precipitate  is  formed,  collect  the  precipitate  on  a  filter, 
wash  and  dry  it. 

Calcium  sulphate,  CaSO1  =  136  (Dried  gypsum,  Plaster-of-Paris, 
Calcined  plaster).  It  has  been  mentioned  above  that  the  mineral 
gypsum  is  native  calcium  sulphate  in  combination  with  2  molecules 


CALCIUM.  155 

of  water  of  crystallization.  By  heating  to  about  115°  C.  (239°  F.) 
most  of  this  water  is  expelled,  and  a  nearly  anhydrous  sulphate 
formed.  This  article  readily  recombines  with  water,  becoming  a 
hard  mass,  for  which  reason  it  is  used  for  making  moulds  and  casts, 
and  in  surgery.  If  the  gypsum  is  heated  to  a  considerably  higher 
temperature  than  the  one  mentioned,  all  water  is  expelled,  and  the 
product  thus  obtained  combines  with  water  but  very  slowly. 

Tricalcium  phosphate,  Calcii  phosphas  praecipitatus,  Ca3(PO4)2 
=  310  (Precipitated  calcium  phosphate,  Phosphate  of  Time,  Bone- 
phosphate).  By  dissolving  bone-ash  (bone  from  which  all  organic 
matter  has  been  expelled  by  heat)  in  hydrochloric  acid,  and  precipi- 
tating the  solution  with  ammonia  water  there  is  obtained  calcium 
phosphate,  which  contains  traces  of  calcium  fluoride  and  magnesium 
phosphate. 

A  pure  article  is  made  by  precipitating  a  solution  of  calcium 
chloride  by  sodium  phosphate  and  ammonia : 

2Xa2HPO,  +  SCaCL,  +  2NH4OH  =  Ca^POJ.,  +  4NaCl  +  2NH4C1  +  2H2O. 

It  is  a  white,  tasteless,  amorphous  powder,  insoluble  in  cold  water, 
soluble  in  hydrochloric  or  nitric  acids. 

Superphosphate,  or  acid  phosphate  of  lime.  Among  the  inorganic  sub- 
stances which  serve  as  plant-food,  calcium  phosphate  is  a  highly  important 
one.  As  this  compound  is  found  usually  in  very  small  quantities  as  a  con- 
stituent of  the  soil,  and  as  this  small  quantity  is  soon  removed  by  the  various 
crops  taken  from  a  cultivated  soil,  it  becomes  necessary  to  replace  it  in  order 
to  enable  the  plant  to  grow  and  to  form  seeds. 

For  this  purpose  the  various  phosphatic  rocks  (chiefly  calcium  phosphate) 
are  converted  into  commercial  fertilizers,  which  is  accomplished  by  the  addi- 
tion of  sulphuric  acid  to  the  ground  rock.  The  sulphuric  acid  removes  from 
the  tricalcium  phosphate  one  or  two  atoms  of  calcium,  forming  mono-  or 
dicalcium  phosphate  and  calcium  sulphate.  The  mixture  of  these  substances, 
containing  also  the  impurities  originally  present  in  the  phosphatic  rocks,  is 
sold  as  acid  phosphate  or  superphosphate. 

Bone-black  and  bone-ash.  Phosphates  enter  the  animal  system 
in  the  various  kinds  of  food,  and  are  to  be  found  in  every  tissue  and 
fluid,  but  most  abundantly  in  the  bones  and  teeth.  Bones  contain 
about  30  per  cent,  of  organic  and  70  per  cent,  of  inorganic  matter, 
most  of  which  is  tricalcium  phosphate.  When  bones  are  burned  until 
all  the  organic  matter  has  been  destroyed  and  volatilized,  the  result- 
ing product  is  known  as  bone-ash.  If,  however,  the  bones  are  sub- 
jected to  the  process  of  destructive  distillation  (heating  with  exclusion 


156  METALS  AND  THEIR  COMBINATIONS. 

of  air),  the  organic  matter  suffers  decomposition,  many  volatile 
products  escape,  and  most  of  the  non-volatile  carbon  remains  mixed 
with  the  inorganic  portion  of  the  bones,  which  substance  is  known 
as  bone-black  or  animal  charcoal. 

Calcium  hypophosphite,  Calcii  hypophosphis,  Ca(PH2O2)2  = 
17O.  Obtained  by  heating  pieces  of  phosphorus  with  milk  of  lime 
until  hydrogen  phosphide  ceases  to  escape.  From  the  filtered  liquid 
the  excess  of  lime  is  removed  by  carbon  dioxide,  and  the  clear  liquid 
evaporated  to  dryness.  (Great  care  must  be  taken  during  the  whole 
of  the  operation,  which  is  somewhat  dangerous  on  account  of  the 
inflammable  and  explosive  nature  of  the  compounds.) 

8P  +  6H2O  +  3[Ca(OH)2]  =  3[Ca(PH2O2)2]  +  2PH3. 

Calcium  hypophosphite  is  generally  met  with  as  a  white,  crystal- 
line powder  wkh  a  pearly  lustre ;  it  is  soluble  in  6  parts  of  water 
and  has  a  neutral  reaction  to  litmus. 

Calcium  chloride,  Calcii  chloridum,  CaCl2  =  11O.8,  and 
Calcium  bromide,  Calcii  bromidum,  CaBr2  =  199.6,  may  both 
be  obtained  by  dissolving  calcium  carbonate  in  hydrochloric  acid  or 
hydrobromic  acid,  until  the  acids  are  neutralized.  Both  salts  are 
highly  deliquescent. 

Chlorinated  lime,  Calx  chlorata  (Bleaching -powder,  incorrectly 
called  Chloride  of  lime).  This  is  chiefly  a  mixture  (according  to  some, 
a  compound)  of  calcium  chloride  with  calcium  hypochlorite,  and  is 
manufactured  on  a  very  large  scale  by  the  action  of  chlorine  upon 
calcium  hydroxide : 

2Ca(OH)2    +    4C1  =  2H2O  +  Ca(ClO)2  +  CaCl2. 
Calcium  hydroxide.  Chlorinated  lime. 

Bleaching-powder  is  a  white  powder,  having  a  feeble  chlorine-like 
odor ;  exposed  to  the  air  it  becomes  damp  from  absorption  of  moist- 
ure, undergoing  decomposition  at  the  same  time;  with  dilute  acids  it 
evolves  chlorine,  of  which  it  should  contain  not  less  than  35  per  cent. 
in  available  form.  The  action  of  hydrochloric  acid  takes  place  thus : 

Ca(C10)2  -f  2HC1  =  CaCl2  -f  2HC1O; 
2HC10  +  2HC1  =  2H20  +  4C1. 

Bleaching-powder  is  a  powerful  disinfecting  and  bleaching  agent. 

Sulphurated  lime,  Calx  sulphurata,  is  a  mixture  of  calcium 
sulphide  and  sulphate,  obtained  by  heating  to  redness  in  a  crucible  a 


CALCIUM.  157 

mixture  of  dried  calcium  sulphate,  starch,  and  charcoal  until  the 
contents  have  lost  their  black  color.  By  the  deoxidizing  action  of 
coal  and  starch  the  larger  portion  of  calcium  sulphate  is  converted 
into  sulphide. 

Analytical  reactions. 
(Calcium  chloride,  CaClg,  may  be  used.) 

1.  Add  to  solution  of  a  calcium  salt,  the  carbonate  of  either  potas- 
sium, sodium,  or  ammonium:  a  white  precipitate  of  calcium  carbon- 
ate, CaCO3,  is  produced. 

2.  Add  sodium  phosphate  to  neutral  solution  of  calcium  :  a  white 
precipitate  of  calcium  phosphate,  CaHPO4,  is  produced. 

3.  Add  ammonium  (or  potassium)  oxalate  to  a  calcium  solution :  a 
white  precipitate  of  calcium  oxalate,  CaC2O4,  is  produced,  which  is 
insoluble  in  acetic,  soluble  in  hydrochloric  acid. 

4.  Sulphuric  acid  or  soluble  sulphates  produce  a  white  precipitate 
of  calcium  sulphate,  CaSO4,  in  concentrated,  but  not  in  dilute  solu- 
tions of  calcium. 

5.  Add  potassium  or  sodium  hydroxide :    a  white  precipitate  of 
calcium  hydroxide,  Ca(OH)2,  is  produced  in  concentrated,  but  not  in 
diluted  solutions.     Ammonia  water  gives  no  precipitate. 

6.  Calcium  compounds  impart  a  reddish-yellow  color  to  the  flame. 

Stontium,  Sr11  =  87.3.  Found  in  a  few  localities  in  the  minerals 
strontianite,  SrCO3,  and  celestite,  SrSO4.  Its  compounds  resemble 
those  of  calcium  and  barium.  The  oxide,  SrO,  cannot  be  obtained 
easily  by  heating  the  carbonate,  as  this  is  much  more  stable  than 
calcium  carbonate.  It  may,  however,  be  readily  prepared  by  heating 
the  nitrate.  The  hydroxide,  Sr(OH)2,  is  formed  when  the  oxide  is 
brought  in  contact  with  water;  it  is  more  soluble  than  calcium 
hydroxide. 

Strontium  nitrate,  Sr(NO3)2,  Strontium  chloride,  SrCl2,  Strontium 
bromide,  SrBr2,  and  Strontium  iodide,  SrI2,  may  be  obtained  by  dis- 
solving the  carbonate  in  the  respective  acids.  The  nitrate  is  used 
extensively  for  pyrotechnic  purposes,  as  strontium  imparts  a  beau- 
tiful red  color  to  flames  ;  the  bromide  and  iodide  are  official. 

Analytical  reactions. 
(Strontium  nitrate,  Sr(NO3)2,  may  be  used.) 

1.  The  reactions  of  strontium  with  soluble  carbonates,  oxalates,  and 
phosphates  are  analogous  to  those  of  calcium. 


158  METALS  AND  THEIR  COMBINATIONS. 

2.  Add  calcium  sulphate :  a  white  precipitate  of  strontium  sul- 
phate, SrSO4,  is  formed  after  a  few  minutes. 

3.  Add  sulphuric  acid  or  a  soluble  sulphate :  a  white  precipitate 
forms  at  once  in  concentrated,  after  a  while  in  dilute  solutions. 

4.  Add  potassium  chromate;  a  pale-yellow  precipitate  of  stron- 
tium chromate,  SrCrO4,  is  formed,  which  is  soluble  in  acetic  acid 
and  in  hydrochloric  acid.     (Potassium  dichromate  causes  no  precipi- 
tation.) 

5.  Strontium  compounds  color  the  flame  beautifully  red. 
Barium,  Bau  =  136.9.     Occurs  in  nature  chiefly  as  sulphate  in 

barite  or  heavy  spar,  BaSO4,  but  also  as  carbonate  in  witherite,  BaCO3. 
Barium  and  its  compounds  resemble  closely  those  of  calcium  and 
strontium. 

Barium  chloride,  BaCl2  +  2H2O,  is  prepared  by  dissolving  the 
carbonate  in  hydrochloric  acid.  It  crystallizes  in  prismatic  plates, 
and  is  used  as  a  valuable  reagent. 

Barium  dioxide  or  peroxide,  BaO2,  is  made  by  heating  the  oxide  to 
a  dark -red  heat  in  the  air  or  in  oxygen.  When  heated  above  the  tem- 
perature at  which  it  is  formed,  decomposition  into  oxide  and  oxygen 
takes  place.  This  power  to  absorb  oxygen  from  air  and  to  give  it  up 
again  at  a  higher  temperature  has  been  used  as  a  method  of  preparing 
oxygen  on  the  large  scale.  Unfortunately,  the  barium  oxide  cannot 
be  used  for  an  unlimited  number  of  operations,  as  it  loses  the  power 
to  absorb  oxygen  after  it  has  been  heated  several  times.  The  use 
made  of  barium  dioxide  in  preparing  hydrogen  dioxide  has  been 
mentioned  before. 

Barium  dioxide  is  a  heavy,  grayish-white,  amorphous  powder, 
almost  insoluble  in  water,  with  which,  however,  it  forms  a  hydroxider 
and  to  which  it  imparts  an  alkaline  reaction. 

Barium  oxide,  BaO,  is  made  by  heating  barium  nitrate,  Ba(lS"O3)2,, 
which  itself  is  made  by  dissolving  barium  carbonate  in  nitric  acid. 

Barium  salts  are  poisonous ;  antidotes  are  sodium  and  magnesium 
sulphate. 

Analytical  reactions. 
(Barium  chloride,  BaCl2,  may  be  used.) 

1.  The  reactions  of  strontium  with  soluble  carbonates,  oxalates, 
and  phosphates  are  analogous  to  those  of  calcium  solutions. 

2.  Add  sulphuric  acid  or  soluble  sulphates  :  a  white  precipitate  of 
barium  sulphate,  BaSo4,  is  produced   immediately,  even   in  dilute 
solutions.     The  precipitate  is  insoluble  in  all  diluted  acids. 


ALUMINUM. 


159 


3.  Add  calcium   sulphate  :    a  white  precipitate,  insoluble  in  all 
diluted  acids,  is  formed  immediately. 

4.  Add  potassium  chromate  or  dichromate  :  a  pale-yellow  precipi- 
tate of  barium  chromate,  BaCrO4,  is  formed,  which  is  soluble  in 
hydrochloric  acid. 

5.  Barium  compounds  color  the  flame  yellowish-green. 

Summary  of  analytical  characters  of  the  alkaline  earth-metals. 


Magnesium. 

Calcium. 

Strontium. 

Barium. 

Potassium  dichromate 

Yellow  pre- 

Yellow pre- 

cipitate. 

Calcium  sulphate 

cipitate. 
White  pre- 

cipitate 
White  pre- 

Ammonium carbonate  .  . 
Ammonium  hydroxide  . 

White  preci- 
pitate soluble 
in  NH4C1. 
White  pre- 

White pre- 
cipitate. 

cipitate  form- 
ing slowly 
White  pre- 
cipitate. 

cipitate  form- 
ing at  once. 
White  pre- 
cipitate. 

Ammonium  oxalate  .  .  . 

Sodium  phosphate  .  .  . 
Flame  color 

cipitate 
No  precipi 
tate  unless 
very  con- 
centrated 
White  pre- 
cipitate. 

White  pre- 
cipitate in 
dilute 
solution 
White  pre- 
cipitate. 

White  pre- 
cipitate in 
strong 
solution. 
White  pre- 
cipitate. 
Red 

White  pre- 
cipitate in 
strong 
solution. 
White  pre- 
cipitate 

red. 

green. 

24.     ALUMINUM. 

Aliii  27  (27.04). 

Aluminum  is  the  representative  of  the  metals  of  the  earths  proper ; 
all  other  members  of  this  class  are  found  in  nature  in  very  small 

QUESTIONS. — 221.  Which  metals  form  the  group  of  the  alkaline  earths,  and 
in  what  respect  do  their  compounds  differ  from  those  of  the  alkali-metals  ? 
222.  How  is  calcium  found  in  nature  ?  223.  What  is  burned  lime ;  from  what, 
and  by  what  process  is  it  made,  and  how  does  water  act  on  it  ?  224.  What  is 
lime-water ;  how  is  it  made,  and  what  are  its  properties  ?  225.  Mention  some 
varieties  of  calcium  carbonate  as  found  in  nature,  and  how  is  it  obtained  by 
an  artificial  process  from  the  chloride?  226.  What  is  Plaster-of-Paris,  and 
what  is  gypsum ;  what  are  they  uesd  for  ?  227.  State  composition  and  mode  of 
manufacturing  bleaching-powder ;  what  are  its  properties,  and  how  do  acids  act 
upon  it?  228.  What  is  bone-black,  bone-ash,  acid  phosphate,  and  precipitated 
tricalcium  phosphate  ?  How  are  they  made  ?  229.  Give  tests  for  barium,  calcium 
and  strontium;  how  can  they  be  distinguished  from  each  other?  230.  Which 
compounds  of  barium  and  strontium  are  of  interest,  and  what  are  they  used  for? 


160  METALS  AND  THEIR  COMBINATIONS. 

quantities,  and  are  chiefly  of  scientific  interest,  with  the  exception  of 
cerium,  which  furnishes  an  official  preparation. 

Occurrence  in  nature.  Aluminum  is  found  almost  exclusively 
in  the  solid  mineral  portion  of  the  earth ;  rarely  more  than  traces  of 
aluminum  compounds  are  found  dissolved  in  water,  and  the  occur- 
rence of  aluminum  in  either  the  vegetable  or  animal  organism  seems 
to  be  purely  accidental. 

By  far  the  largest  quantity  of  aluminum  is  found  in  combination 
with  silicic  acid  in  the  various  silicated  rocks  forming  the  greater 
mass  of  our  earth,  such  as  feldspar,  slate,  basalt,  granite,  mica,  horn- 
blende, etc.,  or  in  the  various  modifications  of  clay  formed  by  their 
decomposition. 

The  minerals  known  as  corundum,  ruby,  sapphire,  and  emery,  are 
aluminum  oxide  in  a  crystallized  state,  and  more  or  less  colored  by 
traces  of  other  substances. 

Metallic  aluminum  may  be  obtained  by  the  decomposition  of 
aluminum  chloride  by  metallic  sodium  : 

A12C16  +  6Na  =  6NaCl  -f  2A1. 

It  is  now  manufactured  by  the  electrolysis  of  aluminum  and  sodium 
fluoride. 

Aluminum  is  an  almost  sil  vej>whi  tew  metal  of  a  very  low  specific 
gravity  (2.67) ;  it  is  capable  of  assuming  a  high  polish,  and  for  this 
reason  is  used  for  ornamental  articles ;  it  is  very  strong,  yet  malleable, 
and  does  not  change  in  dry  or  moist  air. 

Some  of  the  alloys  of  aluminum  are  now  used  in  the  arts,  as,  for 
instance,  aluminum-bronze,  an  alloy  resembling  gold  and  composed 
of  10  parts  of  aluminum  with  90  of  copper. 

Aluminum  is  trivalent,  and  shows,  like  a  number  of  other  elements 
(iron,  chromium,  etc.),  the  peculiarity  that  the  double  atom  Al2vi  acts 
as  a  single  sexivalent  atom. 

Alum  is  the  general  name  for  a  group  of  isomorphous  salts,  com- 
posed of  one  molecule  of  the  sulphate  of  a  univalent  metal  in  combi- 
nation with  one  molecule  of  the  sulphate  of  a  trivalent  metal, 
combined  in  crystallizing  with  24  molecules  of  water.  The  general 
formula  of  an  alum  is  consequently  Mi2SO4Miii2(SO4)3.24H2O  or 
Mi2Miii2(SO4)4.24H2O.  M1  represents  in  this  case  a  univalent,  Mai  a 
trivalent  metal. 


ALUMINUM.  161 

Alums  known  are,  for  instance  : 

Potassium-aluminum  sulphate,  K2SO4,  A12(SO4)3.24H2O. 

Ammonium-aluminum  sulphate,  (NH4)2SO4,  A12(SO4)3  24H2O. 

Potassium-chromium  sulphate,  K2SO4,  Cr2(SO4)3.24H2O. 

Ammonium-ferric  sulphate,  (NH4)2SO4,  Fe2(SO4)3.24H2O. 

The  official  alum,  alumen,  is  the  potassium  alum,  a  white  substance 
crystallizing  in  large  octahedrons,  soluble  in  10  parts  of  cold  and  0.3 
part  of  boiling  water ;  this  solution  has  an  acid  reaction  and  a 
sweetish  astringent  taste. 

Alum  is  manufactured  on  a  large  scale  by  decomposing  certain 
kinds  of  clay  (aluminum  silicates)  by  sulphuric  acid,  when  aluminum 
sulphate  is  formed,  to  the  solution  of  which  potassium  or  ammonium 
sulphate  is  added,  when,  on  evaporation,  potassium  or  ammonium 
alum  crystallizes. 

Dried  alum,  Alumen  exsiccatum,  K2SO4.A12(SO4)3  =  516. 
(Burnt  alum.)  This  is  common  alum,  from  which  the  water  of  crys- 
tallization has  been  expelled  by  heat.  It  is  a  white  powder,  dis- 
solving very  slowly  in  cold,  but  quickly  in  boiling  water. 

Aluminum  hydroxide,  A12  (OH)6  =  156.  Obtained  by  adding 
water  of  ammonia  or  solution  of  sodium  carbonate  to  solution  of 
alum,  when  aluminum  hydroxide  is  precipitated  in  the  form  of  a 
highly  gelatinous  substance,  which,  after  being  well  washed,  is  dried 
at  a  temperature  not  exceeding  40°  C.  (104°  F.). 

K2S04.A12(S04)3  +  6NH4OH  =  K2SO4  4-  3[(NH4)2SO4]  -f-  A12(OH)6; 
K2SO4A12(S04)3  +  3Na2CO3  +  3H2O  =  K2SO4  +  3Na2SO4  +  3CO2  +  A12(OH)6. 

The  usual  decomposition  between  a  soluble  carbonate  and  any  soluble  salt 
{provided  decomposition  takes  place  at  all)  is  the  formation  of  an  insoluble 
carbonate ;  according  to  this  rule,  the  addition  of  a  soluble  carbonate  to  alum 
should  produce  aluminum  carbonate.  The  basic  properties  of  aluminum 
oxide,  however,  are  so  weak  that  it  is  not  capable  of  uniting  with  so  weak  an 
acid  as  carbonic  acid,  and  it  is  for  this  reason  that  the  decomposition  takes 
place  as  shown  by  the  above  formula,  with  liberation  of  carbon  dioxide, 
whilst  the  hydroxide  is  formed.  (Other  metals,  the  oxides  of  which  have  weak 
basic  properties,  show  similar  reactions,  as,  for  instance,  chromium,  and  iron  in 
the  ferric  salts.) 

The  weak  basic  properties  of  aluminum  are  shown  also  by  the  fact  that  alu- 
minum sulphate,  chloride,  and  nitrate,  and  even  alum  itself,  have  an  acid 
reaction,  while  the  corresponding  salts  of  the  alkalies  or  alkaline  earths  are 
neutral. 

Aluminum  hydroxide  shows  considerable  surface-attraction  toward  many 
substances,  which  property  is  made  use  of  in  the  art  of  dyeing,  where  the 
hydroxide  is  used  for  retaining  coloring  matter  upon  the  cotton-fibre.  Prac- 

11 


162  METALS  AND  THEIR  COMBINATIONS. 

tically  this  is  accomplished  by  precipitating  aluminum  hydroxide  from  solutions 
containing  coloring  matter,  which  latter  is  carried  down  and  precipitated  upon 
the  fibre  by  the  aluminum  hydroxide ;  or  by  impregnating  the  articles  to  be 
dyed  with  this  compound  and  placing  them  in  the  colored  solutions. 

Experiment  25.  Dissolve  10  grammes  of  sodium  carbonate  in  100  c.c.  of 
water,  heat  it  to  boiling,  and  add  to  it,  with  constant  stirring,  a  hot  solution, 
made  by  dissolving  10  grammes  of  alum  in  100  c.c.  of  water.  Wash  the  pre- 
cipitate first  by  decantation,  and  then  upon  a  filter,  until  the  washings  are  not 
rendered  turbid  by  barium  chloride.  Dry  a  portion  of  the  precipitate  at  a  low 
temperature,  and  use  as  aluminum  hydroxide.  Mix  a  small  quantity  of  the 
wet  precipitate  with  a  decoction  of  logwood  (made  by  boiling  about  0.2 
grammes  of  logwood  with  50  c.c.  of  water),  agitate  for  a  few  minutes,  and 
filter.  Notice  that  the  red  color  of  the  solution  has  entirely  disappeared,  or 
nearly  so,  in  consequence  of  the  great  surface-attraction  of  the  aluminum 
hydroxide  for  coloring  matter. 

Aluminum  oxide,  A12O3  (Alumina),  is  obtained  as  a  white, 
tasteless  powder  either  by  burning  the  metal  or  by  expelling  the 
water  from  the  hydroxide  by  heat  : 

A12(OH)6  =  A12O3  +  3H2O. 

Aluminum  sulphate,  Alumini  sulphas,  A12(SO4)3.16H2O=630. 
A  white  crystalline  powder,  soluble  in  about  its  weight  of  water, 
obtained  by  dissolving  the  oxide  or  hydroxide  in  sulphuric  acid  and 
evaporating  the  solution  to  dryness  over  a  water-bath. 
A12(OH)6  +  3H2S04  ==  A12(S04)3  +  6H2O. 

Aluminum  chloride,  A12C16.  This  compound  is  of  interest  on 
account  of  being  the  salt  from  which  the  metal  was  formerly  obtained. 
Most  chlorides  may  be  obtained  by  dissolving  the  metal,  its  oxide, 
hydroxide,  or  carbonate  in  hydrochloric  acid.  Accordingly  aluminum 
chloride  may  be  obtained  in  solution  : 

A12(OH)6  +  6HC1  =  A12C16  +  6H2O. 

On  evaporating  the  solution  to  dryness,  however,  and  heating  the 
dry  mass  further  with  the  view  of  expelling  all  water,  decomposition 
takes  place,  hydrochloric  acid  escapes,  and  aluminum  oxide  is  left : 

A12C16  -f  3H2O  =  A1203  -f  6HC1. 

Aluminum  chloride,  consequently,  cannot  be  obtained  in  a  pure 
state  (free  from  water)  by  this  process,  but  it  may  be  made  by  expos- 
ing to  the  action  of  chlorine  a  heated  mixture  of  aluminum  oxide 
and  carbon.  Neither  carbon  nor  chlorine  alone  causes  any  decompo- 


ALUMINUM.  163 

sition  of  the  aluminum  oxide,  but  by  the  united  efforts  of  these  two 
substances  decomposition  is  accomplished  : 

A1203  4-  30  +  6C1  =  SCO  +  AL^CV 

Clay  is  the  name  applied  to  a  large  class  of  mineral  substances, 
differing  considerably  in  composition,  but  possessing  in  common  the 
two  characteristic  features  of  plasticity  and  the  predominance  of 
aluminum  silicate  in  combination  with  water. 

The  various  kinds  of  clay  have  been  formed  in  the  course  of  time  from  such 
double  silicates  as  feldspar  and  others,  by  a  process  which  is  partly  of  a 
mechanical,  partly  of  a  chemical  nature,  and  consists  chiefly  in  the  disintegra- 
tion of  rocks  and  a  removal  of  potassium  and  sodium  by  the  chemical  action  of 
carbonic  acid,  water,  and  other  agents. 

The  various  kinds  of  clay  are  used  in  the  manufacture  of  bricks,  earthenware, 
stoneware,  porcelain,  etc.  The  process  of  burning  these  substances  accom- 
plishes the  hardening  by  expelling  water  which  is  present  in  the  clay.  Pure 
clay  is  white ;  the  red  color  of  the  common  varieties  is  due  to  the  presence  of 
ferric  oxide.  For  china  or  porcelain,  clay  is  used  containing  silicates  of  the 
alkalies  which,  in  burning,  melt,  causing  the  production  of  a  more  homogo- 
neous  mass,  while  in  common  earthenware  the  pores,  produced  by  expelling 
the  moisture,  remain  unfilled. 

Glass  is  similar  in  composition  to  the  better  varieties  of  porcelain. 
All  varieties  of  glass  are  mixtures  of  fusible,  insoluble  silicates,  made 
by  fusing  silicic  acid  (white  sand)  with  different  metallic  oxides  or 
carbonates,  the  silicic  acid  combining  chemically  with  the  metals. 
Sodium  and  calcium  are  the  chief  metals  in  common  glass,  though 
potassium,  lead,  and  others  also  are  frequently  used.  Color  is  im- 
parted to  the  glass  by  the  addition  of  certain  metallic  oxides,  which 
have  a  coloring  effect,  as,  for  instance,  manganese  violet,  cobalt  blue, 
chromium  green,  etc. 

Ultramarine  is  a  beautiful  blue  substance,  found  in  nature  as  the  mineral 
"  lapis  lazuli,"  which  was  highly  valued  by  artists  as  a  color  before  the  dis- 
covery of  the  artificial  process  for  manufacturing  it. 

Ultramarine  is  now  manufactured  on  a  very  large  scale  by  heating  a  mix- 
ture of  clay,  sodium  sulphate  and  carbonate,  sulphur,  and  charcoal  in  large 
crucibles,  when  decomposition  takes  place  and  the  beautiful  blue  compound 
is  obtained.  As  neither  of  the  substances  used  in  the  manufacture  has  a  ten- 
dency to  form  colored  compounds,  the  formation  of  this  blue  ultramarine  is 
rather  surprising,  and  the  true  chemical  constitution  of  it  is  yet  unknown. 

Ultramarine  is  insoluble  in  water  and  is  decomposed  by  acids  with  libera- 
tion of  hydrogen  sulphide,  which  shows  the  presence  of  sodium  sulphide.  A 
green  ultramarine  is  now  also  manufactured. 


164  METALS  AND  THEIR  COMBINATIONS. 


Analytical  reactions. 

(A  solution  of  aluminum  sulphate,  A12(SO4)3,  or  of  aluminum  chloride, 
A12C16,  may  be  used.) 

1.  To  solution  of  an  aluminum  salt  add   potassium  or  sodium 
hydroxide  :  a  white  gelatinous  precipitate  of  aluminum  hydroxide, 
A12(OH)6,  is  produced,  which  is  soluble  in  excess  of  the  alkali. 

2.  To  aluminum  solution  add  ammonium  hydroxide  :  the  same 
precipitate  as  above  is  obtained,  but  it  is  insoluble  in  an  excess  of  the 
reagent. 

3.  The  carbonates  of  ammonium,  sodium,  or  potassium  produce 
the  same  precipitate  with  liberation  of  carbon  dioxide.     (See  expla- 
nation above.) 

4.  Ammonium  sulphide  produces  the  same  precipitate  with  libera- 
tion of  hydrogen  sulphide : 

A12C16  +  3(NH4)2S  +  6H20  =  A12(OH)6  +  6NH4C1  +  3H2S. 

5.  Sodium  phosphate  produces  a  precipitate  of  aluminum  phos- 
phate, soluble  in  acids. 

Cerium,  Ce  =  141.  This  element  occurs  in  nature  sparingly  in  a  few  rare 
minerals,  chiefly  as  silicate  in  cerite.  In  its  general  deportment  cerium  resem- 
bles aluminum.  Cerous  solutions  give  with  either  ammonium  sulphide,  or 
ammonium  and  sodium  hydroxide,  a  white  precipitate  of  cerous  hydroxide, 
Ce2(OH)6.  Ammonium  oxalate  forms  a  white  precipitate  of  cerous  oxalate, 
Ce2(C2O4)39H2O,  which  is  the  only  official  cerium  preparation.  Cerium  oxa- 
late is  a  white,  granular  powder,  insoluble  in  water  and  alcohol,  but  soluble  in 
hydrochloric  acid.  Exposed  to  a  red  heat  it  is  decomposed  and  converted  into 
reddish-yellow  eerie  oxide.  If  this  oxide,  or  the  residue  obtained  by  heating 
any  cerium  salt  to  red  heat,  is  dissolved  in  concentrated  sulphuric  acid,  and  a 
crystal  of  strychnine  added,  a  deep  blue  color  appears,  which  changes  first  to 
purple  and  then  to  red. 


QUESTIONS.— 231.  Mention  some  varieties  of  crystallized  aluminum  oxide 
found  in  nature  and  some  silicates  containing  it.  232.  Give  the  general 
formula  of  an  alum,  and  mention  some  alums.  233.  Which  alum  is  official, 
how  is  it  made,  what  are  its  properties,  and  what  is  it  used  for?  234.  What 
is  dried  alum,  and  how  does  it  differ  from  common  alum  ?  235.  How  is  alu- 
minum chloride  made,  and  how  is  the  metal  obtained  from  it?  236.  State  the 
properties  of  aluminum.  237.  What  change  takes  place  when  ammonium 
hydroxide,  and  what  change  when  sodium  carbonate  is  added  to  a  solution  of 
alum  ?  238.  What  is  the  composition  of  earthenware,  porcelain,  and  glass ; 
how  and  from  what  materials  are  they  manufactured  ?  239.  What  is  ultra- 
marine? 240.  Give  tests  for  aluminum  compounds. 


IRON. 


165 


Summary  of  analytical  characters  of  the  earth-metals  and 

chromium. 


Aluminum, 

Cerium. 

Chromium. 

Ammonium  sulphide  . 

White  precipitate. 

White  precipitate. 

Green  precipitate. 

Potassium  hydroxide  . 
Ammonia  water  .     .     . 

White  precipitate. 
Soluble  in  KOH. 
Not  re-precipitated 
by  boiling. 
White  precipitate. 

White  precipitate. 
Insoluble  in  KOH 

White  precipitate. 

Green  precipitate. 
Soluble  in  KOH. 
Re-precipitated 
by  boiling. 
Green  precipitate. 

Ammonium  carbonate 

White  precipitate. 

White  precipitate. 

Green  precipitate. 

25.      IRON.     (Ferrum.) 
Feii  =  55.9  (55.88). 

General  remarks  regarding-  the  metals  of  the  iron  group.  The 
six  metals  (Fe,  Co,  M,  Mn,  Cr,  Zn)  belonging  to  this  group  are  distin- 
guished by  forming  sulphides  (chromium  excepted)  which  are  insolu- 
ble in  water,  but  soluble  in  dilute  mineral  acids  ;  they  are,  conse- 
quently, not  precipitated  from  their  neutral  or  acid  solutions  by 
hydrosulphuric  acid,  but  by  ammonium  sulphide  as  sulphides 
(chromium  as  hydroxide);  their  oxides,  hydroxides,  carbonates, 
phosphates,  and  sulphides  are  insoluble ;  their  chlorides,  iodides, 
bromides,  sulphates,  and  nitrates  are  soluble  in  water. 

With  the  exception  of  zinc,  these  metals  are  magnetic ;  they  de- 
compose water  at  a  red  heat,  the  oxide  being  formed  and  hydrogen 
liberated ;  in  dilute  hydrochloric  or  sulphuric  acid  they  dissolve 
with  formation  of  chlorides  or  sulphates,  respectively,  and  liberation 
of  hydrogen. 

With  the  exception  of  zinc,  which  is  bivalent,  the  metals  of  the 
iron  group  are  bivalent  in  some  compounds,  trivalent  in  others,  and 
form  a  number  of  oxides,  the  higher  of  which  show,  in  some  cases, 
decidedly  acid  properties,  as,  for  instance,  chromic  or  manganic 
oxides. 

The  trivalence  of  the  elements  mentioned  is  now  assumed  to  be 
due  to  the  combining  of  two  quadrivalent  atoms  of  these  elements. 
It  is  for  this  reason  that  we  find  in  ferric,  manganic,  or  chromic 
compounds  always  a  double  atom  of  these  elements  exerting  a  valence 
of  six.  The  constitution  of  ferric  chloride,  Fe2Cl6,  and  ferric  oxide, 
Fe2O3,  may  be  graphically  represented  thus  : 


166  METALS  AND  THEIR  COMBINATIONS. 

XC1 

~ 


J, 


Occurrence  in  nature.  Among  all  the  heavy  metals,  iron  is  both 
the  most  useful  and  the  most  widely  and  abundantly  diffused  in 
nature.  It  is  found,  though  usually  in  but  small  quantities,  in  nearly 
all  forms  of  rock,  clay,  sand,  and  earth  ;  its  presence  in  these  being 
indicated  generally  by  their  color  (red,  reddish-brown,  or  yellowish- 
red),  as  iron  is  the  most  common  of  all  natural,  inorganic  coloring 
agents.  It  is  found  also,  though  in  small  quantities,  in  plants,  and 
in  somewhat  larger  proportions  in  the  animal  system,  chiefly  in  the 
blood.  In  the  metallic  state  iron  is  scarcely  ever  found,  except  in 
the  meteorites  or  metallic  masses  which  fall  occasionally  upon  our 
earth  out  of  space. 

The  chief  compounds  of  iron  found  in  nature  are  : 

Hematite,  ferric  oxide,  Fe2O3. 

Magnetic  iron  ore,  ferrous-ferric  oxide,  FeO.Fe2O3. 

Spathic  iron  ore,  ferrous  carbonate,  FeCO3. 

Iron  pyrites,  bisulphide  of  iron,  FeS2. 

The  carbonate  and  sulphate  are  found  sometimes  in  spring  waters, 
which,  when  containing  considerable  quantities  of  iron,  are  called 
chalybeate  waters.  Finally,  iron  is  a  constituent  of  some  organic 
substances  which  are  of  importance  in  the  animal  system. 

Manufacture  of  iron.  There  is  no  other  metal  manufactured  in 
such  immense  quantities  as  iron,  the  use  of  which  in  thousands  of 
different  tools,  machines,  and  appliances  is  highly  characteristic  of 
our  present  age.  Iron  is  manufactured  from  the  above-named  oxides 
or  the  carbonate  by  heating  them  with  coke  and  limestone  in  large 
blast  furnaces,  which  have  a  somewhat  cylindrical  shape,  and  are 
constantly  fed  from  above  with  a  mixture  of  the  substances  named, 
while  hot  air  is  forced  into  the  furnace  through  suitable  apertures 
near  its  hearth.  The  chemical  change  which  takes  place  in  the  upper 
and  less  heated  part  of  the  furnace  is  a  deoxidation  of  the  iron  oxide 

by  the  carbon  : 

Fe203  +  30  =  SCO  +  2Fe 

The  heat  necessary  for  this  decomposition  and  fusion  of  the  re- 
duced iron  is  produced  by  the  combustion  of  the  fuel,  maintained  by 
the  oxygen  of  the  air  blown  into  the  furnace.  At  the  same  time  the 
lime  and  other  bases  combine  with  the  silica  contained  in  the  ore, 


IRON.  167 

forming  a  fusible  glass,  called  cinder  or  slag.  The  iron  and  slag 
collect  at  the  bottom  of  the  furnace,  where  they  separate  by  gravity, 
and  are  run  off  every  few  hours. 

Iron  thus  obtained  is  known  as  cast-iron,  or  pig-iron,  and  is  not 
pure,  but  always  contains,  besides  silicon  (also  sulphur,  phosphorus, 
and  various  metals),  a  quantity  of  carbon  varying  from  2  to  5  per 
cent.  It  is  the  quantity  of  this  carbon  and  its  condition  which  im- 
parts to  the  different  kinds  of  iron  different  properties.  Steel  contains 
from  0.16  to  2  per  cent.,  wrought-  or  bar-iron  but  very  small  quanti- 
ties, of  carbon.  Wrought-iron  is  made  from  cast-iron  by  the  process 
known  as  puddling,  which  is  a  burning-out  of  the  carbon  by  oxida- 
tion, accomplished  by  agitating  the  molten  mass  in  the  presence  of 
an  oxidizing  flame.  Steel  is  made  either  from  cast-iron  by  partially 
removing  the  carbon,  or  from  wrought-iron  by  recombining  it  with 
carbon — i.  e.,  by  agitating  together  molten  wrought-  and  cast-iron  in 
proper  proportions. 

Properties.  The  high  position  which  iron  occupies  among  the  useful  metals 
is  due  to  a  combination  of  valuable  properties  not  found  in  any  other  metal. 
Although  possessing  nearly  twice  as  great  a  tenacity  or  strength  as  any  of  the 
other  metals  commonly  used  in  the  metallic  state,  it  is  yet  one  of  the  lightest, 
its  specific  gravity  being  about  7.7.  Though  being  when  cold  the  least  yield- 
ing or  malleable  of  the  metals  in  common  use,  its  ductility  when  heated  is  such 
that  it  admits  of  being  rolled  into  the  thinnest  sheets  and  drawn  into  the  finest 
wire,  the  strength  of  which  is  so  great  that  a  wire  of  one-tenth  of  an  inch  in 
diameter  is  capable  of  sustaining  700  pounds.  Finally,  iron  is,  with  the  ex- 
ception of  platinum,  the  least  fusible  of  all  the  useful  metals. 

Iron  is  little  affected  by  dry  air,  but  is  readily  acted  upon  by  moist  air,  when 
ferric  oxide  and  ferric  hydroxide  (rust)  are  formed. 

Iron  forms  two  series  of  compounds,  distinguished  as  ferrous  and 
ferric  compounds ;  in  the  former,  iron  is  bivalent,  in  the  latter,  appa- 
rently trivalent,  because,  as  shown  above,  the  double  atom  exerts  a 
valence  of  six.  Almost  all  ferrous  compounds  show  a  tendency  to 
pass  into  ferric  compounds  when  exposed  to  the  air,  or  more  readily 
when  treated  with  oxidizing  agents,  such  as  nitric  acid,  chlorine,  etc. 
As  the  reaction  of  iron  in  ferrous  and  ferric  compounds  differs  con- 
siderably, they  must  be  studied  separately. 

Reduced  iron,  Perrum  reductum.  This  is  metallic  iron,  obtained 
as  a  very  fine,  grayish-black,  lustreless  powder  by  passing  hydrogen 
gas  (purified  and  dried  by  passing  it  through  sulphuric  acid)  over 
ferric  oxide,  heated  in  a  glass  tube  : 

Fe203  +  6H  =  3H2O  +  2Fe. 


168  METALS  AND  THEIR  COMBINATIONS. 

The  official  article  should  have  at  least  80  per  cent,  of  metallic 
iron. 

Ferrous  oxide,  PeO  (Monoxide  or  suboxide  of  iron).  This  com- 
pound is  little  known  in  the  separate  state,  as  it  has  (like  most  ferrous 
compounds)  a  great  tendency  to  absorb  oxygen  from  the  air.  The 
ferrous  hydroxide,  Fe(OH)2,  may  be  obtained  by  the  addition  of  any 
alkaline  hydroxide  to  the  solution  of  any  ferrous  salt,  when  a  white 
precipitate  is  produced  which  rapidly  turns  bluish-green,  dark-gray, 
black,  and  finally  brown,  in  consequence  of  absorption  of  oxygen 
(see  Plate  I.,  2) : 

FeSO4  +  2NH4OH  =  (NH4)2SO4  +  Fe(OH)2; 
2Fe(OH)2  +  O  +  H20  =  Fe2(OH)6. 

The  precipitation  of  ferrous  hydroxide  is  not  complete,  some  iron 
always  remaining  in  solution. 

Ferrous  oxide  is  a  strong  base,  uniting  with  acids  to  form  salts, 
which  have  usually  a  pale-green  color. 

Ferric  oxide,  Fe2O3.     A  reddish-brown  powder,  which  may  be 
obtained  by  heating  ferric  hydroxide  to  expel  water : 
Fe2(OH)6  =a  Fe2O3  -f  3H2O. 

It  is  a  feeble  base ;  its  salts  show  usually  a  brown  color. 

Ferric  hydroxide,  Ferric  hydrate,  Ferri   oxidum  hydratum, 
Fe2(OH)6  =213.8  (Hydrated  oxide  of  iron.  Per-  or  sesqui-oxide,  Red 
oxide  of  iron),  is  obtained  by  precipitation  of  ferric  sulphate  or  ferric 
chloride  by  ammonium  or  sodium  hydroxide  (see  Plate  I.,  3) : 
Fe2(S04)3  +  6NH4OH  =  3[(NH4)2SOJ  +  Fe2(OH)6. 

Precipitation  is  complete,  no  iron  remaining  in  solution  as  in  the 
case  of  ferrous  salts. 

Ferric  hydroxide  is  a  reddish-brown  powder,  sometimes  used  as 
an  antidote  in  arsenic  poisoning ;  for  this  purpose  it  is  not  used  in 
the  dry  state,  but  after  having  been  freshly  precipitated  and  washed, 
it  is  mixed  with  water,  and  this  mixture  used.  Kecently  precipitated 
and  consequently  highly  divided  ferric  hydroxide  combines  more 
readily  with  arsenous  acid  than  the  hydroxide  which  has  been  kept 
some  time,  or  which  has  been  dried,  and  thereby  assumed  a  denser 
condition. 

Hydrated  oxide  of  iron  with  magnesia,  U.  S.  P.,  is  a  mixture  made  by  adding 
magnesia  to  a  solution  of  ferric  sulphate,  when  magnesium  sulphate  and  ferric 


IRON.  169 

hydroxide  are  formed ;  the  two  substances  are  not  separated  from  each  other, 
the  mixture  being  intended  for  immediate  administration  as  an  antidote  in 
cases  of  arsenic  poisoning. 

Ferrous-ferric  oxide,  PeO.Pe2O3  (Magnetic  oxide).  This  com- 
pound, which  shows  strong  magnetic  properties,  has  been  mentioned 
above  as  one  of  the  iron  ores,  and  is  known  as  loadstone.  It  has  a 
metallic  lustre  and  iron-black  color,  and  is  produced  artificially  by 
the  combustion  of  iron  in  oxygen,  or  in  the  hydrated  state  by  the 
addition  of  ammonium  hydroxide  to  a  mixture  of  solutions  of  ferrous 
and  ferric  salts. 

Iron  trioxide,  PeO3.  Not  known  in  a  separate  state,  but  in  com- 
bination with  alkalies.  In  these  compounds,  called  ferrates,  FeO3 
acts  as  an  acid  oxide,  analogous  to  chromium  trioxide,  CrO3,  in  chro- 
mates.  The  composition  of  potassium  ferrate  is  K2FeO4. 

Ferrous  Chloride,  FeCl2  (Protochloride  of  iron),  is  obtained  as  a 
pale-green  solution  by  dissolving  iron  in  hydrochloric  acid : 
Fe  +  2HC1  =  FeCl2  +  2H. 

By  evaporation  of  the  solution,  the  dry  salt  may  be  obtained.  The 
solution  and  salt  absorb  oxygen  very  readily : 

3FeCl2  -f  O  =  FeO  +  Fe2CI6. 
Ferric  chloride,  ferrous,  and  afterward  ferric  oxide,  are  formed. 

Ferric  chloride,  Ferri  chloridum,  Fe2Cl6.12H2O  =  54O.2  (Chlo- 
ride, sesqui-chloride,  or  perchloride  of  iron),  is  obtained  by  adding  to 
the  solution  of  ferrous  chloride  (obtained  as  mentioned  above)  hydro- 
chloric and  nitric  acids  in  sufficient  quantities,  and  applying  heat 
until  complete  oxidation  has  taken  place.  The  nitric  acid  oxidizes 
the  hydrogen  of  the  hydrochloric  acid  to  water,  while  the  chlorine 
combines  with  the  ferrous  chloride,  nitrogen  dioxide  being  formed 

also: 

6FeCl2  +  2HN03  +  6HC1  =  3Fe2Cl6  +  4H2O  -f  2NO. 

By  sufficient  evaporation  of  the  solution,  ferric  chloride  is  obtained 
as  a  crystalline  mass  of  an  orange-yellow  color;  it  is  very  deli- 
quescent, has  an  acid  reaction,  and  a  strongly  styptic  taste.  The 
water  of  crystallization  cannot  be  expelled  by  heat,  because  heat 
decomposes  the  salt,  free  hydrochloric  acid  and  ferric  -  oxide  being 
formed. 

Experiment  26.  Dissolve  by  the  aid  of  heat  1  gramme  of  fine  iron  wire  in 
about  4  c.c.  of  hydrochloric  acid,  previously  diluted  with  2  c.c.  of  water* 


170  METALS  AND  THEIR  COMBINATIONS. 

Filter  the  warm  solution  of  ferrous  chloride,  mix  it  with  2  c.c.  of  hydrochloric 
acid,  and  add  to  it  slowly  and  gradually  about  0.6  c.c.  of  nitric  acid.  Evap- 
orate in  a  fume  chamber  as  long  as  red  vapors  escape ;  then  test  a  few  drops 
with  potassium  ferricyanide,  which  should  not  give  a  blue  precipitate ;  if  it 
does,  the  solution  has  to  be  heated  with  a  little  more  nitric  acid  until  the  con- 
version into  ferric  chloride  is  complete  and  the  potassium  ferricyanide  pro- 
duces no  precipitate.  Ferric  chloride  thus  obtained  may  be  mixed  with  4  c.c. 
of  hot  water  and  set  aside,  when  it  forms  a  solid  mass  of  Fe2Cl6.12H2O.  How 
much  FeCl2,  how  much  Fe2Cl6,  and  how  much  Fe2Cl6.12H20  can  be  obtained 
from  1  gramme  of  iron? 

Solution  of  chloride  of  iron,  Liquor  ferri  chloridi,  U.  S.  P. 
This  is  a  solution  in  water,  containing  37.8  per  cent,  of  the  anhydrous 
ferric  chloride  and  some  free  hydrochloric  acid.  It  is  a  reddish- 
brown  liquid  of  specific  gravity  1.405,  having  the  taste  and  reaction 
of  the  dry  salt.  This  solution,  mixed  with  3  volumes  of  alcohol 
and  left  standing  in  a  closed  vessel  for  at  least  three  months,  forms 
the  tincture  of  chloride  of  iron,  Tinctura  ferri  chloridi,  U.  S.  P.  By 
the  action  of  the  alcohol  on  ferric  chloride  this  is  reduced  to  the 
ferrous  state,  while  at  the  same  time  a  number  of  other  compounds 
are  formed,  imparting  to  the  liquid  an  ethereal  odor. 

Dialyzed  iron  is  an  aqueous  solution  of  about  5  per  cent,  of  ferric 
hydroxide  with  some  ferric  chloride.  It  is  made  by  slowly  adding 
to  a  solution  of  ferric  chloride,  ammonium  hydroxide  as  long  as  the 
precipitate  of  ferric  hydroxide  formed  is  redissolved  in  the  ferric 
chloride  solution,  on  shaking  violently.  The  clear  solution  thus 
obtained  is  placed  in  a  dialyzer  floating  in  water,  which  latter  is 
renewed  every  day  until  it  shows  no  reaction  with  silver  nitrate. 
The  ammonium  chloride  passes  through  the  membrane  of  the  dialyzer 
into  the  water,  while  all  iron  as  hydroxide  with  some  chloride  is  left 
in  solution. 

The  combination  of  an  oxide  or  hydroxide  with  a  normal  salt  is 
called  usually  a  basic  salt  or  oxy-salt ;  dialyzed  iron  is  a  highly  basic 
oxychloride  of  iron. 

Ferrous  iodide,  PeI2.  When  water  is  poured  upon  a  mixture  of 
metallic  iron  (fine  wire  is  best)  and  iodine,  the  two  elements  combine 
directly,  forming  a  pale-green  solution  of  ferrous  iodide,  from  which 
the  salt  may  be  obtained  by  evaporation.  As  it  is  oxidized  and 
decomposed  easily  by  the  action  of  the  air,  an  official  preparation, 
the  saccharated  ferrous  iodide,  U.  S.  P.,  is  made  by  adding  about  80 
parts  of  sugar  of  milk  to  20  parts  of  ferrous  iodide ;  the  sugar  pre- 
vents, to  some  extent,  rapid  oxidation. 


IRON.  171 

Experiment  27.  Cover  some  fine  iron  wire  with  water,  heat  gently,  and  add 
iodine  in  fragments  as  long  as  the  red  color  of  iodine  disappears.  Notice  that 
the  iron  is  dissolved  gradually,  the  result  of  the  reaction  being  the  formation 
of  a  pale-green  solution  of  ferrous  iodide. 

Ferrous  bromide,  PeBr2.  Made  analogously  to  ferrous  iodide, 
by  the  action  of  bromine  on  metallic  iron. 

Ferrous  sulphide,  FeS.  Easily  obtained  as  a  black,  brittle  mass, 
by  heating  iron  filings  with  sulphur,  when  the  elements  combine.  It 
is  used  chiefly  for  liberating  hydrogen  sulphide,  by  the  addition  of 
sulphuric  acid.  Iron  combines  with  sulphur  in  several  proportions; 
some  of  these  iron  sulphides  are  found  in  nature. 

Ferrous  sulphate,  Ferri  sulphas,  FeSO4.7H2O  =  277.9  (Sul- 
phate of  iron,  G-reen  vitriol,  Copperas).  Obtained  by  dissolving  iron 
in  dilute  sulphuric  acid,  evaporating,  and  crystallizing : 

Fe  +  H2S04  =  2H  +  FeSO4. 

Also  obtained  as  a  by-product  in  some  branches  of  chemical  indus- 
try, and  by  heap-roasting  of  the  native  iron  sulphide : 
FeS2  +  6O  =  FeS04  +  SO2. 

Ferrous  sulphate  crystallizes  in  large,  bluish-green  prisms;  it  is 
soluble  in  water,  insoluble  in  alcohol.  Exposed  to  the  air,  it  loses 
water  of  crystallization,  and  absorbs  oxygen. 

The  dried  ferrous  sulphate,  U.  S.  P.,  is  made  by  expelling  about 
4  molecules  of  water  by  heating  to  100°  C.  (212°  F.);  the  granu- 
lated (precipitated)  ferrous  sulphate  is  made  by  pouring  a  strong  aque- 
ous solution  of  ferrous  sulphate,  slightly  acidulated  with  sulphuric 
acid,  into  alcohol,  when  ferrous  sulphate  separates  as  a  crystalline 
powder,  which  is  washed  and  dried. 

Ferric  sulphate,  Fe2(SO4)3.  The  solution  of  this  salt,  Liquor 
Jerri  tersulphatis,  Solution  of  ferric  sulphate,  U.  S.  P.,  is  made  by 
adding  sulphuric  and  nitric  acids  to  a  solution  of  ferrous  sulphate 
and  heating : 

6FeSO4  +  3H2SO,  +  2HNO3  =  3[Fe2(SOJ3]  -f  2NO  +  4H2O. 

The  action  of  nitric  acid  is  similar  to  that  described  above  under 
ferric  chloride.  The  hydrogen  of  the  sulphuric  acid  is  oxidized,  and 
the  radical  SO4  unites  with  the  ferrous  sulphate,  nitrogen  dioxide 
being  liberated. 

Solution  of  ferric  sulphate  is  used   in  the  preparation  of  Ferric 


172  METALS  AND  THEIR  COMBINATIONS. 

ammonium  sulphate,  Fern  et  ammonii  sulphas,  (NH4)2SO4.Fe2(SO4)3. 
24H2O  (iron  alum  or  ammonio-ferric  alum),  which  is  made  by  mixing 
solution  of  ferric  sulphate  with  ammonium  sulphate  and  crystallizing. 
The  salt  has  a  pale  violet  color  and  is  readily  soluble  in  water. 

Solution  of  ferric  subsulphate,  Liquor  ferri  subsulphatis 
(Monsel's  solution).  This  is  a  solution  similar  to  the  preceding,  but 
contains  less  sulphuric  acid,  and  is,  therefore,  looked  upon  as  a  basic 
ferric  sulphate,  of  the  doubtful  composition  5[Fe2(SO4)3].Fe2(OH)6. 

Ferric  nitrate,  Fe2(NO3)6.     A  6  per  cent,  solution  of  this  salt  is 
official,  under  the  name  Solution  of  ferric  nitrate.  Liquor  ferri  nitratis, 
U.  S.  P.,  and  is  made  by  dissolving  ferric  hydroxide  in  nitric  acid  : 
Fe2(OH)6  +  6HN03  =  6H2O  +  Fe2(NO3)6. 

It  is  an  amber-colored,  or  reddish,  acid  liquid. 

Ferrous  carbonate,  FeCO3.  Occurs  in  nature  ;  may  be  obtained 
by  mixing  solutions  of  ferrous  sulphate  and  sodium  carbonate  or 
bicarbonate  : 


FeSO4  +  2NaHCO3  =  Na2SO4  +  FeCO3 

The  precipitate  is  first  nearly  white,  but  soon  assumes  a  gray  color 
from  oxidation.  The  saecharated  carbonate  of  iron,  U.  S.  P.,  is  made 
by  mixing  the  washed  precipitate  with  sugar,  and  drying.  The 
sugar  prevents,  to  some  extent,  rapid  oxidation.  The  preparation 
contains  15  per  cent,  of  ferrous  carbonate. 

Ferric  carbonate  does  not  exist,  the  affinity  between  the  feeble  ferric 
oxide  and  the  weak  carbonic  acid  not  being  sufficient  to  unite  them 
chemically. 

Ferrous  phosphate,  Fe3(PO4)2.  When  sodium  phosphate  is 
added  to  solution  of  ferrous  sulphate,  a  precipitate  of  the  composi- 
tion FeHPO4  is  formed  : 

Na2HPO4  -f  FeSO4  =  FeHPO4  +  Na^O,. 

If,  however,  sodium  acetate  is  added,  a  precipitate  of  the  composi- 
tion Fe3(PO4)2  is  formed  : 

3FeSO4  +  2Na2HPO4  =  Fe3(PO4)2  +  2Na2SO4  +  H2SO4. 

The  sulphuric  acid  liberated,  as  shown  in  this  formula,  decomposes 
the  sodium  acetate,  forming  sodium  sulphate  and  free  acetic  acid. 
Ferrous  phosphate  is  a  slate-colored  powder,  absorbing  oxygen 
readily,  becoming  darker  in  color. 


IRON. 


173 


Analytical  reactions. 


1.  Ammonium  sul- 
phide. 


2.  HydrosulpTiuric 
acid. 


3.  Ammonium,  so- 
dium, or  potas- 
sium hydroxide 


4.  Ammonium,  so- 
dium, or  potas- 
sium carbonate. 


5.  Alkali  phosphates 

or  arsenates 

6.  Potassium  ferro- 

cyanide. 

K4Fe(CN)6. 


7.  Potassium  ferri- 

cyanide. 

K6Fe2(CN)12. 

8.  Tannic  acid. 


.  Potassium  sul- 
phocyanate. 
KCNS. 


Ferrous  salts. 

(Use  FeSO4.) 

Black  precipitate  of   ferrous 
sulphide  (Plate  I.,  1). 
FeS04+(NH4)2S  = 

(NH4)2S04 

No  change. 


White  precipitate  of  ferrous 
hydroxide  soon  turning 
green,  black,  and  brown. 
Precipitation  not  complete 
(Plate  I.,  2). 

FeCl2  4-  2NaOH  = 
2NaCl+    Fe(OH)2. 

White  precipitate  of  ferrous 
carbonate,  soon  turning 
darker. 


2NaCl  +  FeCO3. 

Almost  white  precipitate,  soon 
turning  darker. 

Almost  white  precipitate,  soon 
turning  blue  by  absorption 
of  oxygen  (Plate  I.,  4). 


Blue  precipitate  of  ferrous  ferri 

cyanide,  or  TurnbulFs  blue. 

3FeCl2  4-  K6Fe2(CN)12  = 

6KC1    4- Fe3Fe2(CN)12. 

No  change,  provided  oxidation 
of  the  ferrous  salt  has  not 
taken  place. 

As  above. 


Ferric  salts. 

(Use  Fe2Cl6.) 

Black  precipitate  of  ferrous  sul- 
phide mixed  with  sulphur. 
Fe2Cl6  +  3[(NH4)2S]  = 
6NH4C1  4-  2FeS  4  S. 

Ferric  salts  are  converted  into 
ferrous  salts  with  precipita- 
tion of  sulphur. 

Fe2Cl64-   H2S  = 
2FeCl2  +  2HC1  +  S. 

Reddish-brown   precipitate   of 
ferric  hydroxide      Precipita- 
tion is  complete  (Plate  1 ,  3). 
Fe2Cl6  4-  6(NH4OH)  = 
6NH4Cl4-Fe2(OH)6. 


Reddish-brown  precipitate   of 
ferric  hydroxide,  with  libera- 
tion of  carbon  dioxide  (Plate 
I,  3). 
Fe2Cl6  +  SNa^COg  +  3H2O  = 

6NaCl  4  Fe2(OH)6+  3CO2. 

A  yellowish-white  precipitate 
is  produced. 

Dark-blue  precipitate  of  ferric 
ferrocyanide,  or  Prussian  blue. 
Decomposed  by  alkalies;  in- 
soluble in  acids  (Plate  I.,  5). 

2Fe2Cl6  +  3[K4Fe(CNj6]  = 
12KC1  4-  Fe43[Fe(CN)6]. 

No  precipitate  is  produced,  but 
the  liquid  is  darkened  to  a 
greenish-brown  hue. 

A  dark  greenish-black  precipi- 
tate of  ferric  tannate  is  pro- 
duced (Plate  VII.,  3). 

Deep  blood-red  precipitate  of 
ferric  sulphocyanate  (Plate  I., 
6.) 


174  METALS  AND  THEIE  COMBINATIONS. 

Ferric  phosphate,  Fe2(PO4)2,  may  be  obtained  from  ferric  chloride 
solution  by  precipitation  with  an  alkali  phosphate.  The  soluble 
ferric  phosphate  of  the  U.  S.  P.  is  a  scale  compound.  (See  index.) 

Ferric  hypophosphite,  Ferri  hypophosphis,  Fe2(H2PO2)6  = 
501.8  (Hypophosphite  of  iron).  Made  by  dissolving  ferric  hydroxide 
in  hypophosphorous  acid,  and  evaporating.  It  is  a  grayish- white 
powder,  slightly  soluble  in  water,  soluble  in  hydrochloric  acid,  in 
hypophosphorous  acid,  and  in  a  warm,  concentrated  solution  of  an 
alkali  citrate. 

26.    MANGANESE— CHKOMIUM— COBALT— NICKEL. 

Manganese,  Mn  =  54.8.  Manganese  is  found  either  as  dioxide 
(Black  oxide  of  manganese,  pyrolusite),  MnO2,  or  as  sesquioxide, 
Mn2O3.  In  small  quantities  it  is  a  constituent  of  many  minerals. 

Metallic  manganese  resembles  iron  in  its  physical  and  chemical 
properties,  and  may  be  obtained  by  reducing  the  carbonate  with 
charcoal.  Manganese  is  darker  in  color  than  iron,  considerably 
harder,  and  somewhat  more  easily  oxidized. 

Oxides  of  manganese.  Four  well-defined  compounds  of  man- 
ganese with  oxygen  are  known  in  the  separate  state,  and  two  others 
only  in  combination  with  other  elements.  These  oxides  are  : 

Manganous  oxide  (monoxide  or  protoxide),  MnO. 

Manganous  manganic  oxide,  MnO  Mn2O3— Mn3O4. 

Manganic  oxide  (sesquioxide),  Mn2O3. 

Manganese  dioxide  (binoxide,  peroxide,  black  oxide),  MnO2. 

Manganic  acid,       1  Not  known  in  a  separate  state,     {  **£  +  ^nO,. 
Permanganic  acid,  >  «.  H2O  -f-  Mn2O7. 

QUESTIONS. — 241.  Which  metals  belong  to  the  "iron  group/'  and  what  are 
their  general  properties  ?  242.  How  is  iron  found  in  nature,  and  what  com- 
pounds are  used  in  its  manufacture?  243.  Describe  the  process  for  manufac- 
turing iron  on  a  large  scale,  and  state  the  difference  between  cast-iron, 
wrought-iron,  steel,  and  reduced  iron.  244.  State  the  composition  and  mode 
of  preparation  of  ferrous  and  ferric  hydroxides.  What  are  their  properties? 
245.  Describe  in  words  and  chemical  symbols  the  process  for  making  ferric 
chloride.  What  is  tincture  of  chloride  of  iron  ?  246.  How  are  ferrous  iodide 
and  bromide  made?  247.  State  the  properties  of  ferrous  sulphate.  Under 
what  other  names  is  it  known,  and  how  is  it  made?  248.  What  change  takes 
place  when  soluble  carbonates  are  added  to  soluble  ferrous  and  ferric  salts? 
249.  Mention  agents  by  which  ferrous  compounds  may  be  converted  into  ferric 
compounds,  and  these  into  ferrous  compounds.  Explain  the  chemical  changes 
taking  place.  250.  Mention  tests  for  ferrous  and  ferric  compounds. 


IRON.       COBALT.      NICKEL. 


Ferrous  sulphide,  precipitated 
from  ferrous  solutions  by  ammonium 
sulphide. 


Ferrous  hydroxide  passing  into 
ferric  hydroxide.  Ferrous  solutions 
precipitated  by  alkali  hydroxides. 


Ferric  hydroxide,  precipitated 
from  ferric  solutions  by  alkali  hydrox- 
ides. 


Ferrous   solutions,  precipitated 
by  potassium  ferrocyanide. 


Ferric  solutions,  precipitated  by 
potassium  ferrocyanide,  or,  Ferrous 
solutions  precipitated  by  potassium 
ferricyanide. 


Ferric    solutions,   treated    with 
alkali  sulphocyanates. 


Cobaltous  carbonate,  precipita- 
ted from  cobaitous  solutions  by  so- 
dium carbonate. 


Nickeloits  carbonate,  precipita- 
ted from  nickelous  solutions  by  sodium 
carbonate. 


MANGANESE—  CHROMIUM—  COBALT—NICKEL.  175 

Manganous  oxide  is  a  greenish-gray  powder,  obtainable  by  heating 
the  carbonate  ;  or  as  a  nearly  white  hydroxide  by  precipating  a  man- 
ganous  salt  by  sodium  hydroxide.  It  is  a  strong  base,  saturating 
acids  completely,  and  forming  salts  which  have  generally  a  rose 
color  or  a  pale  reddish  tint. 

Manganese  dioxide,  Mangani  oxidum  nigrum,  MnO2  =  86.8. 
This  is  by  far  the  most  important  compound  of  manganese,  as  it  is 
largely  used  for  generating  chlorine  : 

MnO2  +  4HC1  =  MnCl2  -f  2H2O  +  2C1. 

It  is  a  heavy,  grayish-black,  crystalline  mineral,  liberating  oxygen 
when  heated  to  redness  : 

3MnO2  =  Mn3O4  +  2O. 

The  official  article  should  contain  at  least  66  per  cent,  of  MnO2. 

Manganous  sulphate,  Mangani  sulphas,  MnSO4.4H2O  =  222.8, 
may  be  obtained  by  dissolving  the  oxide  or  dioxide  in  sulphuric 
acid  ;  in  the  latter  case  oxygen  is  evolved  : 

Mn02  +  H2S04  =  MnS04  +  H2O  +  O. 

As  manganese  dioxide  generally  contains  iron  oxide,  the  solution 
contains  sulphates  of  both  metals.  By  evaporating  to  dryness  and 
strongly  igniting,  the  iron  salt  is  decomposed.  The  ignited  mass  is 
now  lixivated  with  water,  and  the  filtered  solution  evaporated  for 
crystallization. 

It  is  an  almost  colorless,  or  pale  rose-colored  substance,  isomor- 
phous  with  the  sulphates  of  magnesium  and  zinc  ;  it  is  easily  soluble 
in  water. 

Potassium  permanganate,  Potassii 


157.8.  Whenever  a  compound  (any  oxide  or  salt)  of  manganese  is 
fused  with  alkali  carbonates  (or  hydroxides)  and  alkali  nitrates  (or 
chlorates)  the  manganese  is  converted  into  manganic  acid,  which 
combines  with  the  alkali,  forming  potassium  (or  sodium)  manganate: 
3MnO2  +  3K2CO3  +  KC1O3  =  3K2MnO4  +  3CO,  +  KC1.  . 

The  fused  mass  has  a  dark-green  color,  and  when  dissolved  in 
water  gives  a  dark  emerald  -green  solution,  from  which,  by  evapora- 
tion, green  crystals  of  potassium  manganate  may  be  obtained. 

The  green  solution  is  decomposed  easily  by  any  acid  (or  even  by 
water  in  large  quantity)  into  a  red  solution  of  potassium  perman- 
ganate and  a  precipitate  of  manganese  dioxide. 

3K2MnO4  +  2H2SO4  =  MnO2  +  2K2SO4  -f  2KMnO4  +  2H2O. 


176  METALS  AND  THEIR  COMBINATIONS. 

By  evaporation  and  crystallization  potassium  permanganate  is  ob- 
tained in  slender,  prismatic  crystals,  of  a  dark- purple  color,  and  a 
somewhat  metallic  lustre.  The  solution  in  water  has  a  deep  purple, 
or,  when  highly  diluted,  a  pink  color  (Plate  II. ,  1).  It  is  a  power- 
ful oxidizing  agent,  and  an  excellent  disinfectant,  both  properties 
being  due  to  the  facility  with  which  a  portion  of  the  oxygen  is  given 
off  to  any  substance  which  has  affinity  for  it.  If  the  oxidation 
takes  place  in  the  absence  of  an  acid,  a  lower  oxide  of  manganese  is 
formed,  which  separates  as  an  insoluble  substance.  If  an  acid  is 
present,  both  the  potassium  and  manganese  combine  with  it,  forming 
salts,  thus  : 

2(KMnO4)  4-  6HC1  +  x  =  2KC1  +  2MnCl2  +  3H2O  +  xO5. 

x  represents  here  any  substance  capable  of  combining  with  oxygen 
while  in  solution. 

Experiment  28.  Heat  in  a  porcelain  crucible  a  mixture  of  2  grammes  man- 
ganese dioxide,  2  grammes  potassium  hydroxide,  and  1  gramme  potassium 
chlorate,  until  the  fused  mass  has  turned  dark-green.  Dissolve  the  cooled 
mass  with  water,  filter  the  green  solution  of  potassium  manganate,  and  pass 
carbon  dioxide  through  it  until  it  has  assumed  a  purple  color,  showing  that 
the  conversion  into  permanganate  is  complete.  Notice  that  the  acidified  solu- 
tion is  readily  decolorized  by  ferrous  salts  and  other  deoxidizing  agents. 

Analytical  reactions. 
(Manganous  sulphate,  MnSO4,  may  be  used.) 

1.  Ammonium  sulphide  produces  a  yellowish-pink  or  flesh-colored 
precipitate  of  hydrated  manganous  sulphide,  MnS.H2O,  soluble  in 
acetic  and  in  mineral  acids  (Plate  II. ,  2) : 

MnSO4  4-  (NH4)2S  =  (NH4)2SO4  +  MnS. 

2.  Ammonium  (or  sodium)  hydroxide  produces  a  white  precipitate 
of  manganous  hydroxide,  which  soon  darkens  by  absorption  of  oxygen 
(Plate  II.,  3)  and  dissolves  in  oxalic  acid  with  a  rose-red  color : 

MnCl2  +  2NH4OH  =  2NH4C1  +  Mn(OH)2. 

3.  Sodium  (or  potassium)  carbonate  produces  a  nearly  white  pre- 
cipitate of  manganous  carbonate : 

MnSO4  +  Na.2COs  B=  Na2SO4  +  MnCO3. 

4.  Any  compound  of  manganese  heated  on  platinum  foil  with  a 
mixture  of  sodium  carbonate  and  nitrate  forms  a  bluish-green  mass, 
giving  a  green  solution  in  water,  which  turns  red  on  addition  of  an 
acid.     (See  explanation  above.) 


MANGANESE— CHROMIUM-COBALT— NICKEL.  177 

5.  Manganese  compounds  fused  with  borax  on  a  platinum  wire 
give  a  violet  color  to  the*  borax  bead. 

6.  Traces  of  manganese  may  be  detected  by  boiling  with  dilute 
nitric  acid  and  red  lead,  when  the  solution  acquires  a  reddish-purple 
color  due  to  the  formation  of  permanganic  acid. 

Chromium,  Or  =  52.  Found  in  nature  almost  exclusively  as 
chromite,  or  chrome-iron  ore,  FeO.Cr2O3,  a  mineral  analogous  in 
composition  to  magnetic  iron  ore,  FeO.Fe2O3.  The  name  chromium, 
from  the  Greek  XP^O-  (chroma),  color,  was  given  to  this  metal  on 
account  of  the  beautiful  colors  of  its  different  compounds,  none  of 
which  is  colorless.  Chromium  forms  two  basic  oxides,  CrO  and 
Cr2O3,  and  an  acid  oxide,  CrO3,  the  combinations  and  reactions  of 
which  have  to  be  studied  separately.  While  chromium  is  closely 
allied  to  aluminum  and  iron  on  one  side,  it  also  shows  a  resemblance 
to  sulphur,  as  indicated  by  the  trioxide,  CrO3,  and  the  acid,  H2CrO4, 
which  are  analogous  to  SO3  and  H2SO4.  Moreover,  the  barium  and 
lead  salts  of  chromic  and  sulphuric  acids  are  both  insoluble. 

Potassium  dichromate,  Potassii  bichromas,  K2Cr2O7  =  294 
(Bichromate  or  red  chromate  of  potassium).  This  salt  is  by  far  the 
most  important  of  all  chromium  compounds,  and  is  the  source  from 
which  they  are  obtained. 

Potassium  dichromate  is  manufactured  on  a  large  scale  by  expos- 
ing a  mixture  of  the  finely  ground  chrome-iron  ore  with  potassium 
carbonate  and  calcium  hydroxide  to  the  heat  of  an  oxidizing  flame 
in  a  reverberatory  furnace,  when  both  constituents  of  the  ore  become 
oxidized,  ferric  oxide  and  chromic  acid  being  formed,  the  latter 
combining  with  the  potassium,  forming  normal  potassium  chromate, 
K2CrO4. 

2(FeOCr2O3)  +  4K2CO3  +  7O  =  Fe2O3  +  4CO2  +  4(K2CrOJ. 

By  treating  the  furnaced  mass  with  water  a  yellow  solution  of 
potassium  chromate  is  obtained,  which,  upon  the  addition  of  sul- 
phuric acid,  is  decomposed  into  potassium  dichromate  and  potassium 
sulphate : 

2(K2Cr04)  +  H2S04  =  K2Cr2O7  +  K2SO4  +  H2O. 

The  two  salts  may  be  separated  by  crystallization.  Potassium 
dichromate  forms  large,  orange-red,  transparent  crystals,  which  are 
easily  soluble  in  water;  heated  by  itself  oxygen  is  evolved,  heated 
with  hydrochloric  acid  chlorine  is  liberated,  heated  with  organic 
matter  or  reducing  agents  these  are  oxidized. 

12 


178  METALS  AND  THEIR  COMBINATIONS. 

To  explain  the  constitution  of  dichromates  we  have  to  assume 
that  chromic  anhydride,  CrO3,  is  capable  of  forming  two  acids  : 

CrO3  +  H2O  =  H2CrO4    =  Chromic  acid. 
2CrO3  +  H2O  =  H2Cr207  =  Dichromic  acid. 

Chromium  trioxide,  Acidum  Chromicum,  CrO3  =  1OO  (Chromic 
acid,  Chromic  anhydride),  is  prepared  by  adding  sulphuric  acid  to  a 
saturated  solution  of  potassium  dichromate,  when  chromium  trioxide 
separates  in  crystals  : 

K2Cr207  +  H2S04  =  K2S04  +  H2O  +  2CrO3. 

Thus  prepared,  its  forms  deep  purplish-red,  needle-shaped  crystals, 
which  are  deliquescent,  and  very  soluble  in  water ;  it  is  powerfully 
corrosive,  and  one  of  the  strongest  oxidizing  agents ;  the  solution  in 
water  has  strong  acid  properties ;  it  combines  with  metallic  oxides, 
forming  chromates  and  dichromates. 

Experiment  29.  Dissolve  a  few  grammes  of  potassium  dichromate  in  water 
and  add  to  4  volumes  of  the  cold  saturated  solution  5  volumes  of  strong  sul- 
phuric acid ;  chromium  trioxide  separates  on  cooling.  Collect  the  crystals  on 
asbestos,  wash  them  with  a  little  nitric  acid,  and  dry  them  by  passing  warm 
dry  air  through  a  tube  in  which  they  have  been  placed  for  this  purpose. 

Chromic  oxide,  Cr2O3  (Sesquioxide  of  chromium),  is  obtained  by 
heating  potassium  dichromate  with  sulphur,  when  potassium  sulphate 
and  chromic  oxide  are  formed  : 

K2Cr2O7  -f  S  =  K2SO4  +  Cr2O3. 

By  washing  the  heated  mass  with  water,  the  chromic  oxide  is  left 
as  a  green  powder,  which  is  insoluble  in  water  and  in  acids ;  it  is  a 
basic  oxide  combining  with  acids  to  form  salts  ;  it  is  used  as  a  green 
color,  especially  in  the  manufacture  of  painted  glass  and  porcelain. 

Chromic  hydroxide,  Cr2(OH)6.  A  solution  of  potassium  dichro- 
mate may  be  deoxidized  by  the  action  of  hydrosulphuric  acid,  sul- 
phurous acid,  alcohol,  or  any  other  deoxidizing  agent,  in  the  presence 
of  sulphuric  or  hydrochloric  acid  : 

K2Cr2O7  +  4H2SO4  +  3H2S  =  K2SO4  +  7H2O  +  38  +  Cr2(SOJ3. 

As  shown  by  this  formula,  the  sulphates  of  potassium  and  chro- 
mium are  formed  and  remain  in  solution,  while  sulphur  is  precipi- 
tated, the  hydrogen  of  the  hydrosulphuric  acid  having  been  oxidized 
and  converted  into  water. 

By  adding  ammonium  hydroxide  to  the  solution  thus  obtained, 


MANGANESE— CHROMIUM— COBALT— NICKEL.  179 

chromic  hydroxide  is  precipitated  as  a  bluish-green  gelatinous  sub- 
stance : 

Cr,(S04)8  +  6NH4OH  ==  3[(NH4)2SOJ  +  Cr2(OH)6. 

By  dissolving  this  hydroxide  in  the  different  acids,  the  various 
salts,  such  as  chloride,  Cr2Cl6,  sulphate,  etc.,  are  obtained.  Chromic 
sulphate,  similar  to  aluminum  sulphate,  combines  with  potassium  or 
ammonium  sulphate  and  water,  forming  chrome  alum,  K2SO4.Cr2 
(SO4)324H2O ;  it  is  a  purple  salt,  and  is  isomorphous  with  other 
alums. 

Analytical   reactions. 

a.   Of  chromic  acid  or  chromates. 

(Use  potassium  chromate,  K2CrO4.) 

1.  Hydrogen  sulphide  added  to  an  acidified  solution  of  a  chromate 
changes  the  red  color  into  green  with  precipitation  of  sulphur.     The 
solution  now  contains  chromium  in  the  basic  form.     (See  explanation 
above.)     (Plate  II.,  4.)     The  conversion  of  chromic  acid  into  oxide 
is  more  readily  accomplished  by  heating  the  chromic  solution  with 
alcohol  and  hydrochloric  acid ;  the  alcohol  is  partly  oxidized,  being 
converted  into  aldehyde. 

2.  Soluble  lead  salts  produce  a  yellow  precipitate  of  lead  chromate 
(chrome  yellow),  PbCrO4,  insoluble  in  acetic,  soluble  in  hydrochloric 
acid  and  in  sodium  hydroxide  (Plate  II.,  6) : 

K2Cr04  +  Pb(NO3)2  =  PbCrO,  +  2KNO3. 

3.  Barium  chloride  produces  a  pale  yellow  precipitate  of  barium 
chromate,  BaCrO4  : 

K2Cr04  +  BaCl2  =r  BaCrO,  +  2KC1. 

4.  Silver  nitrate  produces  a  dark-red  precipitate  of  silver  chromate, 
AgaCrO4  (Plate  II.,  8): 

2AgNO3  +  K2CrO4  =  2KNO3  +  Ag2CrO4. 

5.  Mercurous  nitrate  produces  a  red  precipitate  of  mercurous  chro- 
mate, Hg2CrO4. 

b.   Of  salts  of  chromium. 
(Use  chrome-alum  or  chromic  chloride,  Cr2Cl6.) 

6.  To  chromic  chloride  or  sulphate  add  ammonium  hydroxide  or 
ammonium  sulphide  :  in  both  cases  the  green  hydroxide  of  chromium, 
Cr2(OH)6,  is  precipitated  (Plate  II.,  5)  : 

Cr2Cl6  +  3[(NH4)2S]  +  6H2O  =  6NH4C1  +  3H2S  +  Cr2(OH)6. 


180  METALS  AND  THEIR  COMBINATIONS. 

7.  Potassium  or  sodium  hydroxide  causes  a  similar  green  precipi- 
tate of  chromic   hydroxide,   which   is  soluble   in  an  excess  of  the 
reagent,  but  is  re-precipitated  on  boiling  for  a  few  minutes. 

c.   Of  chromium  in  any  form. 

8.  Compounds  of  chromium,  when  mixed  with  sodium  (or  potas- 
sium) carbonate  and  nitrate,  give,  when  heated  upon  platinum  foi4,  a 
yellow  mass  of  the  alkali  chromate. 

9.  Compounds  of  chromium  impart  a  green  color  to  the  borax 
bead. 

Cobalt  and  Nickel,  Co  ==  58.7,  Ni  =  58.6.  These  two  metals  show  much 
resemblance  to  each  other  in  their  chemical  and  physical  properties,  and  occur 
in  nature  often  associated  with  each  other  as  sulphides  or  arsenides. 

Both  metals  are  nearly  silver- white ;  the  salts  of  cobalt  show  generally  a  red, 
those  of  nickel  a  green  color.  The  solutions  of  both  metals  give  a  black  pre- 
cipitate of  the  respective  sulphides  on  the  addition  of  ammonium  sulphide. 
Ammonium  hydroxide  produces  in  solutions  of  cobalt  a  blue,  in  solutions  of 
nickel  a  green  precipitate  of  the  hydroxides,  both  of  which  are  soluble  in  an 
excess  of  the  reagent ;  potassium  or  sodium  hydroxide  produces  similar  pre- 
cipitates, which  are  insoluble  in  an  excess. 

Cobalt  is  used  chiefly  when  in  a  state  of  combination  (for  coloring  glass  blue)  ; 
nickel  when  in  the  metallic  state.  (German  silver  is  an  alloy  of  nickel,  copper, 
and  zinc.) 

27.   ZINC. 
Znii  =  65.1. 

Occurrence  in  nature.  Zinc  is  found  chiefly  either  as  sulphide 
(zinc-blende),  ZnS,  or  as  carbonate  (calamine),  ZnCO3 ;  also  it  occurs 
in  combination  with  silicic  acid  as  silicate  and  with  oxygen  as  the  red 
oxide. 

Metallic  Zinc  is  obtained  by  heating  in  retorts  the  oxide  or 
carbonate  mixed  with  charcoal,  when  decomposition  takes  place. 

QUESTIONS. — 251.  How  is  manganese  found  in  nature?  252.  Mention  the 
different  oxides  of  manganese.  What  is  the  binoxide  used  for  ?  253.  What 
is  the  color  of  manganese  salts,  of  manganates,  and  of  permanganates  ?  254. 
How  is  potassium  permanganate  made ;  what  are  its  properties,  and  what  is  it 
used  for  ?  255.  Give  tests  for  manganese.  256.  State  composition  and  prop- 
erties of  potassium  dichromate.  257.  How  is  chromium  trioxide  made ;  what 
are  its  properties  ;  what  is  it  used  for ;  and  under  what  other  name  is  it  known  ? 

258.  By  what  process  may  chromium  sesquioxide  be  converted  into  chromates? 

259.  What  is  the  composition  of  the  oxide  and  hydroxide  of  chromium,  and 
how  are  they  made?     260.  Mention  tests  for  chromates  and  chromium  salts. 


II. 


MANGANESE.       CHROMIUM. 


Potassium  permanganate  solu- 
tion, more  or  less  saturated.  Borax- 
bead  colored  by  manganese. 


Mangaiioug  sulphide,  precipi- 
tated from  manganous  solutions  by 
ammonium  sulphide. 


_ 


Manganous  hydroxide  passing1 
into  the  higher  oxides.  Manganous 
solutions  precipitated  by  alkali  hy- 
droxides. 


Potassium  dichromate  solution 
deoxidized  by  reducing  agents. 


Chromic  hydroxide,  precipitated 

from  chromic  solutions  by  alkali  hy- 
droxides. 


Lead  chromate.  precipitated  from 
soluble  chromates  by  lead  acetate. 


Silver  chromate,  precipitated 
from  neutral  chromates  by  silver  ni- 
trate. 


Mercurotis  chromate,  precipi- 
tated from  neutral  chromates  by  mer- 
curous  solutions. 


ZINC.  181 

The  liberated  metal  is  vaporized,  and  distils  into  suitable  receivers, 
where  it  solidifies. 

Zinc  is  a  bluish-white  metal,  which  slowly  tarnishes  in  the  air, 
becoming  coated  with  a  film  of  oxide  and  carbonate ;  it  has  a  crys- 
talline structure  and  is,  under  ordinary  circumstances,  brittle  ;  when 
heated  to  about  130°-150°  C.  (260°-302°  F.)  it  is  malleable,  and 
may  be  rolled  or  hammered  without  fracture.  Zinc  thus  treated 
retains  this  malleability  when  cold ;  the  sheet-zinc  of  commerce  is 
thus  made.  When  zinc  is  further  heated  to  about  200°  C.  (392°  F.), 
it  loses  its  malleability  and  becomes  so  brittle  that  it  may  be  pow- 
dered ;  at  410°  C.  (760°  F.)  it  fuses,  and  at  a  bright- red  heat  it 
boils,  volatilizes,  and,  if  air  be  not  excluded,  burns  with  a  splendid 
greenish -white  light,  generating  the  oxide. 

Zinc  is  used  by  itself  in  the  metallic  state  or  fused  together  with 
other  metals  (German  silver  and  brass  contain  it) ;  galvanized  iron 
is  iron  coated  with  metallic  zinc. 

Zinc  is  a  bivalent  metal,  forming  but  one  oxide  and  one  series  of 
salts,  all  of  which  have  a  white  color. 

Zinc  oxide,  Zinci  oxidum,  ZnO  =  81.1  (Flores  zinci,  Zinc-white), 
may  be  obtained  by  burning  the  metal,  but  if  made  for  medicinal 
purposes,  by  heating  the  carbonate,  when  carbon  dioxide  and  water 
escape  and  the  oxide  is  left : 

3[Zn(OH)2J.2ZnCO3  =  5ZnO  +  2CO2  +  3H2O. 

It  is  an  amorphous,  white,  tasteless  powder,  insoluble  in  water, 
soluble  in  acids ;  when  strongly  heated  it  turns  yellow,  but  on 
cooling  resumes  the  white  color. 

Zinc  hydroxide,  Zn(OH)2,  is  obtained  by  precipitating  zinc  salts 
with  the  hydroxide  of  sodium  or  ammonium ;  the  precipitate,  how- 
ever, is  soluble  in  an  excess  of  either  of  the  alkali  hydroxides. 

Zinc  chloride,  Zinci  chloridum,  ZnCl2  =  135.9.  Made  by  dis- 
solving zinc  or  zinc  carbonate  in  hydrochloric  acid  and  evaporating 
the  solution  to  dry  ness  : 

Zn  +  2HC1  =  ZnCl2  -f  2H. 

It  is  met  with  either  as  a  white  crystalline  powder,  or  in  white 
opaque  pieces ;  it  is  very  deliquescent  and  easily  soluble  in  water 
and  alcohol ;  it  combines  readily  with  albuminoid  substances ;  it 
fuses  at  about  115°  C.  (239°  F.),  and  is  volatilized,  with  partial 
decomposition,  at  a  higher  temperature. 


182  METALS  AND  THEIR  COMBINATIONS. 

Zinc  bromide,  Zinci  bromidum,  ZnBr2  =  224.7.  Obtained 
analogously  to  the  chloride  by  dissolving  zinc  in  hydrobromic  acid  ; 
it  is  a  white  powder,  resembling  the  chloride  in  its  properties. 

Zinc  iodide,  Zinci  iodidum,  ZnI2  =  318.1.  The  two  elements 
zinc  and  iodine  combine  readily  when  heated  with  water ;  the  color- 
less solution  when  evaporated  to  dryness  yields  a  powder  whose 
physical  properties  resemble  those  of  the  chloride. 

Zinc  carbonate,  Zinci  carbonas  prsecipitatus,  2(ZnCO3).3[Zn 
(OH2)]  =  547.5  (Precipitated  carbonate  of  zinc).  Solutions  of  equal 
quantities  of  zinc  sulphate  and  sodium  carbonate  are  mixed  and 
boiled,  when  a  white  precipitate  is  formed,  which  is  a  mixture  of  the 
carbonate  and  hydroxide  of  zinc,  corresponding  more  or  less  to  the 
formula  given  above. 

5ZnSO4  +  5Na2CO3  +  3H2O  =  3CO2  +  5Na2SO4  +  2(ZnCO3).3[Zn(OH)2]. 

Precipitated  zinc  carbonate  is  a  white,  impalpable  powder,  odorless 
and  tasteless,  insoluble  in  water,  soluble  in  acids  and  in  ammonia 
water. 

Zinc  sulphate,  Zinci  sulphas,  ZnSO4.7H2O  —  287.1  (  White  vit- 
riol), is  obtained  by  dissolving  zinc  in  dilute  sulphuric  acid  : 
H2S04  +  zH20  +  Zn  =  ZnSO4  +  zH2O  +  2H. 

If  zinc  be  added  to  strong  sulphuric  acid,  no  decomposition  takes 
place  :  no  sufficient  explanation  has  as  yet  been  given  for  this  fact. 

Zinc  sulphate  forms  small,  colorless  crystals,  which  are  isomorphous 
with  magnesium  sulphate  ;  it  is  easily  soluble  in  water. 

Experiment  30.  Use  the  liquid  obtained  when  performing  Experiment  2,  or, 
if  not  left,  dissolve  a  few  grammes  of  metallic  zinc  in  dilute  sulphuric  acid, 
filter  the  solution,  evaporate  sufficiently,  and  set  aside  for  crystallization.  Use 
the  zinc  sulphate  thus  obtained  for  the  analytical  reactions.  State  the  quantity 
of  dilute  sulphuric  acid  required  for  dissolving  5  grammes  of  zinc,  and  the 
quantity  of  crystallized  zinc  sulphate  which  may  be  obtained. 

Zinc  phosphide,  Zinci  phosphidum,  Zn3P2  =  257.3.  The  two 
elements  zinc  and  phosphorus  combine  readily  when  the  latter  is 
thrown  upon  melted  zinc,  forming  a  grayish-black  powder,  or 
minutely  crystalline,  friable  fragments,  having  a  metallic  lustre  on 
the  fractured  surface. 

Antidotes.  Soluble  zinc  salts  (sulphate,  chloride)  have  a  poisonous  effect. 
If  the  poison  have  not  produced  vomiting,  this  should  be  induced.  Milk, 


ZINC.  183 

white  of  egg,  or,  still  better,  some  substance  containing  tannic  acid  (with  which 
zinc  forms  an  insoluble  compound)  should  be  given. 


Analytical  reactions. 
(Zinc  sulphate,  ZnSO4,  may  be  used.) 

1.  Add  to  solution  of  a  zinc  salt  ammonium  sulphide;  a  white 
precipitate  of  zinc  sulphide,  ZnS,  is  produced.     (Zinc  sulphide  is  the 
only  white  insoluble  sulphide.) 

ZnSO4  +  (NH4)2S  =  (NH4)2SO4  +  ZnS. 

2.  From  neutral  zinc  solutions,  or  from  solutions  containing  free 
acetic  acid,  hydrogen  sulphide  precipitates  white  zinc  sulphide. 

3.  Add  ammonium,  sodium,  or  potassium  hydroxide  :  a  white  pre- 
cipitate of  zinc  hydroxide,  Zn(OH)2,  is  produced,  soluble  in  excess  of 
the  reagent,  with  the  formation  of  zincates,  such  as  Zn  (OK)2. 

4.  Soluble  carbonates  and  phosphates  give  white  precipitates  in 
neutral  solutions  of  zinc. 

5.  Potassium  ferrocyanide  gives  a  white  precipitate  of  zinc  ferro- 
cyanide.    (This  test  may  be  used  to  distinguish  compounds  of  zinc 
from  those  of  magnesium  or  aluminum.) 

6.  Zinc  is  the  only  heavy  metal  whose  compounds  are  all  colorless. 
The  oxide,  carbonate,  phosphate,  and  ferrocyanide  are  insoluble ;  the 
chloride,  nitrate,  and  sulphate  soluble. 

Cadmium,  Cd  =  111.5.  Found  in  nature  associated  (though  in  very  small 
quantities)  with  the  various  ores  of  zinc,  with  which  metal  it  has  in  common  a 
number  of  physical  and  chemical  properties.  Cadmium  differs  from  zinc  by 
forming  a  yellow  sulphide  (with  hydrosulphuric  acid),  insoluble  in  diluted  acids. 
Oadmium  and  its  compounds  are  of  little  interest  here;  the  yellow  sulphide  is 
used  as  a  pigment,  the  sulphate  and  iodide  sometimes  for  medicinal  purposes. 

QUESTIONS. — 261.  How  is  zinc  found  in  nature,  and  by  what  process  is  it 
obtained  ?  262.  Mention  the  properties  of  metallic  zinc,  and  what  is  it  used 
for?  263.  Mention  two  processes  for  making  zinc  oxide.  264.  How  does  heat 
act  on  zinc  oxide  ?  265.  Show  by  chemical  symbols  the  action  of  hydrochloric 
and  sulphuric  acids  on  zinc.  266.  State  the  properties  of  chloride  and  of 
sulphate  of  zinc  ?  267.  What  is  white  vitriol  ?  268.  Explain  the  formation  of 
precipitated  zinc  carbonate,  and  state  its  composition.  269.  Mention  tests  for 
zinc  compounds.  270.  How  many  pounds  of  crystallized  zinc  sulphate  may 
be  obtained  from  21.7  pounds  of  metallic  zinc  ? 


184 


METALS  AND  THEIR  COMBINATIONS. 


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LEAD-  COPPER- BISMUTH.  185 


28.   LEAD -COPPER-BISMUTH. 

General  remarks  regarding1  the  metals  of  the  lead  group.  The 
six  metals  belonging  to  this  group  (Pb,  Cu,  Bi,  Ag,  Hg,  and  Cd)  are 
distinguished  by  forming  sulphides  which  are  insoluble  in  water, 
insoluble  in  dilute  mineral  acids,  insoluble  in  ammonium  sulphide ; 
consequently  they  are  precipitated  from  neutral,  alkaline,  or  acid 
solutions  by  hydrogen  sulphide  or  ammonium  sulphide. 

The  metals  themselves  do  not  decompose  water  at  any  temperature, 
and  are  not  acted  upon  by  dilute  sulphuric  acid ;  heated  with  strong 
sulphuric  acid,  most  of  these  metals  are  converted  into  sulphates  with 
liberation  of  sulphur  dioxide ;  nitric  acid  converts  all  of  them  into 
nitrates  with  liberation  of  nitrogen  dioxide. 

The  oxides,  iodides,  sulphides,  carbonates,  phosphates,  and  a  few  of 
the  chlorides  and  sulphates  of  these  metals  are  insoluble;  all  the 
nitrates,  and  most  of  the  chlorides  and  sulphates  are  soluble. 

In  regard  to  valence,  they  show  no  uniformity  whatever,  silver 
being  univalent,  copper,  cadmium,  and  mercury  bivalent,  bismuth 
trivalent,  and  lead  either  bivalent  or  quadrivalent. 

Lead,  Pb11  =  206.4  (Plumbum).  This  metal  is  obtained  almost 
exclusively  from  the  native  sulphide  of  lead,  called  galena,  PbS,  by 
roasting  until  it  is  converted  into  oxide,  and  smelting  this  with  coke 
in  a  blast  furnace. 

Lead  owes  its  usefulness  in  the  metallic  state  chiefly  to  its  softness, 
fusibility,  and  resistance  to  acids,  which  properties  are  of  advantage 
in  using  it  for  tubes  or  pipes,  or  in  constructing  vessels  to  hold  or 
manufacture  sulphuric  acid.  Lead  is  a  constituent  of  many  alloys, 
as,  for  instance,  of  type-metal,  solder,  britannia  metal,  shot,  etc. 

Experiment  31.  Dissolve  1  gramme  of  lead  acetate  or  lead  nitrate  in  about 
200  c.c.  of  water,  suspend  in  the  centre  of  the  solution  a  piece  of  metallic  zinc 
and  set  aside.  Notice  that  metallic  lead  is  deposited  slowly  upon  the  zinc  in  a 
crystalline  condition,  whilst  zinc  passes  into  solution,  which  may  be  verified  by 
analytical  methods.  The  chemical  change  taking  place  is  this  : 

Pb(NO3)2  +  Zn  =  Zn(NO3)2  +  Pb. 

The  formation  of  the  crystallized  lead  is  called  generally  a  lead-tree. 

i 

Lead  oxide,  Plumbi  oxidum,  PbO  =  222.4  (Litharge).  Obtained 
by  exposing  melted  lead  to  a  current  of  air,  when  the  metal  is 
gradually  oxidized  with  the  formation  of  a  yellow  powder,  known 
as  massicot;  at  a  high  temperature  this  fuses,  forming  reddish-yellow 


186  METALS  AND  THEIR  COMBINATIONS. 

crystalline  scales,  known  as  litharge  ;  by  heating  still  further  in  con- 
tact with  air,  a  portion  of  the  oxide  is  converted  into  dioxide  (or 
peroxide),  PbO2,  and  a  red  powder  is  formed,  known  as  red  lead  (or 
minium),  which  probably  is  a  mixture  (or  combination)  of  oxide  and 
dioxide  of  lead,  PbO2(PbO)2. 

Lead  oxide  is  used  in  the  manufacture  of  lead  salts,  lead  plaster, 
glass,  paints,  etc. 

Mtric  acid  when  heated  with  red  lead  combines  with  the  oxide, 
while  lead  dioxide,  PbO2,  is  left  as  a  dark-brown  powder,  which,  on 
heating  with  hydrochloric  acid,  evolves  chlorine  (similar  to  man- 
ganese dioxide). 

Lead  nitrate,  Plumbi  nitras,  Pb(NO3)2  =  330.4.  Obtained  by 
dissolving  the  oxide  in  nitric  acid  : 

PbO  +  2HNO3  =  H2O  +  Pb(N03)2. 

Lead  nitrate  is  the  only  salt  of  lead  (with  a  mineral  acid)  which  is 
easily  soluble  in  water ;  it  has  a  white  color,  and  a  sweetish,  astrin- 
gent, and  afterward  metallic  taste. 

Lead  carbonate,  Plumbi  carbonas,  2(PbCO3).Pb(OH)2^773.2 

(  White-lead).  This  compound  may  be  obtained  by  precipitation  of 
lead  nitrate  with  sodium  carbonate,  but  is  manufactured  on  a  large 
scale  directly  from  lead,  by  exposing  it  to  the  simultaneous  action  of 
air,  carbon  dioxide,  and  vapors  of  acetic  acid.  The  latter  combines 
with  the  lead,  forming  a  basic  acetate,  which  is  converted  into  the 
carbonate  (almost  as  soon  as  produced)  by  the  carbon  dioxide  present. 

The  action  of  acetic  acid  on  lead  or  lead  oxide  will  be  considered 
in  connection  with  acetic  acid. 

Lead  carbonate  is  a  heavy,  white,  insoluble,  tasteless  powder  ;  the 
white-lead  of  commerce  frequently  is  found  adulterated  with  barium 
sulphate. 

Lead  iodide,  Plumbi  iodidum,  PbI2  —  459.4  (Iodide  of  lead). 
Made  by  adding  solution  of  potassium  iodide  to  lead  nitrate  (Plate 

III.,  6)': 

Pb(N03)2  +  2KI  =  2KNO3  +  PbI2. 

It  is  a  heavy,  bright  yellow,  almost  insoluble  powder,  which  may 
be  distinguished  from  lead  chromate  by  its  solubility  in  ammonium 
chloride  solution  on  boiling,  lead  chromate  being  insoluble  in  this 
solution. 


LEAD— COPPER— BISMUTH.  187 

Poisonous  properties  and  antidotes.  Compounds  of  lead  are  directly 
poisonous,  and  it  happens,  not  infrequently,  that  water  passing  through  leaden 
pipes  or  collected  in  leaden  tanks  becomes  contaminated  with  lead.  Water 
free  from  air  and  salts  scarcely  acts  on  lead ;  but  if  it  contain  air,  oxide  of  lead 
is  formed,  which  is  either  dissolved  by  the  water  or  is  decomposed  by  the 
nitrates  or  chlorides  present  in  the  water,  the  soluble  nitrate  or  chloride  of  lead 
being  formed. 

If  the  water  contains  carbonates  and  sulphates,  however,  these  will  form 
insoluble  compounds,  producing  a  film  or  coating  over  the  lead,  preventing 
further  contact  with  the  water.  Rain  water,  in  consequence  of  its  containing 
atmospheric  constituents,  and  no  sulphates,  acts  as  a  solvent  on  lead  pipe; 
spring  and  river  waters  generally  do  not. 

Water  containing  lead  will  show  a  dark  color  on  passing  hydrogen  sulphide 
through  it ;  if  the  quantity  present  be  very  small,  the  water  should  be  evapo- 
rated to  -j^jy  or  even  y^y  of  its  original  volume  before  applying  the  test. 

The  constant  handling  of  lead  compounds  is  one  of  the  causes  of  lead 
poisoning  (painters'  colic).  As  an  antidote,  mangesium  sulphate  should  be 
used,  which  forms  with  lead  an  insoluble  sulphate ;  the  purgative  action  of 
magnesia  is  also  useful.  (In  lead  works  workmen  often  drink  water  containing 
a  little  sulphuric  acid.) 


Analytical  reactions. 
(Lead  acetate  or  lead  nitrate,  Pb(NO3)2,  may  be  used.) 

1.  To  a  solution  of  lead  salt  add  hydrogen  sulphide  or  ammonium 
sulphide :  a  black  precipitate  of  lead  sulphide  is  produced  (Plate 

111,1): 

Pb(N03)2  +  H2S  =  2HN03  +  PbS. 

2.  Add  sulphuric  acid  or  soluble  sulphate  :  a  white  precipitate  of 
lead  sulphate  is  formed  : 

Pb(NO3)2  +  Na,SO4  =  2NaNO3  -f-  PbSO4. 

3.  Add  hydrochloric  acid  or  a  soluble  chloride  :  a  white  precipitate 
of  lead  chloride,  PbCl2,  is  produced,  which  dissolves  on  heating  or 
on  the  addition  of  much  water,  as  lead  chloride  is  not  entirely  in- 
soluble.    For  the  same  reason,  the  precipitate  is  not  formed  when 
the  solutions  used  are  highly  dilute. 

4.  Other  reagents  which  give  precipitates  with  lead  solutions  are  : 

Potassium  chromate,  producing  yellow  lead  chromate  (chrome  yellow). 

(Plate  II.,  6.) 

Potassium  iodide,  producing  yellow  lead  iodide.     (Plate  III.,  6.) 
Alkali  carbonates,  producing  white  basic  lead  carbonate. 
Alkali  phosphates,  producing  white  lead  phosphate 

Copper,  Cun  =  63.2  (Cuprum).    Found  in  nature  sometimes  in  the 
metallic  state — generally,  however,  combined  with  sulphur  or  oxygen. 


188  METALS  AND  THEIR  COMBINATIONS. 

The  commonest  copper-ore  is  Copper  pyrites,  a  double  sulphide  of 
copper  and  iron,  Cu2FeS2  or  Cu2S.Fe2S3,  having  the  color  and  lustre 
of  brass  or  gold.  Other  ores  are :  Copper  glance,  cuprous  sulphide, 
having  a  dark-gray  color  and  the  composition  Cu2S ;  malachite,  a 
beautiful  green  mineral,  being  a  carbonate  and  hydroxide  of  copper, 
CuCO3.Cu(OH)2.  Cuprous  and  cupric  oxide  also  are  found  occasion- 
ally. Copper  is  obtained  from  the  oxide  by  reducing  it  with  coke ; 
sulphides  previously  are  converted  into  oxide  by  roasting. 

Copper  is  the  only  metal  showing  a  distinct  red  color ;  it  is  so 
malleable  that,  of  the  metals  in  common  use,  only  gold  and  silver 
surpass  it  in  that  respect ;  it  is  one  of  the  best  conductors  of  heat  and 
electricity,  it  does  not  change  in  dry  air,  but  becomes  covered  with  a 
film  of  green  subcarbonate  when  exposed  to  moist  air. 

Copper  frequently  is  used  in  the  manufacture  of  alloys,  of  which 
the  more  important  are  : 

Copper.  Zinc.  Tin.  Nickel. 

Brass 64  36 

German  silver      ...     51  31  ...  18 

Bell-metal    ....     78  22 

Bronze          ....     80  16  4 

Gun-metal    ....     90  10 

Copper  frequently  is  alloyed  with  gold  and  silver. 

Copper  is  a  bivalent  element,  forming  two  oxides  and  two  series  of 
salts,  distinguished  as  cuprous  and  cupric  compounds ;  the  cuprous 
salts  are  here  but  of  little  interest. 

Cupric  oxide,  CuO  (Black  oxide  or  monoxide  of  copper).  Heated 
to  redness,  copper  becomes  covered  with  a  black  scale,  which  is  cupric 
oxide ;  it  is  obtained  also  by  heating  cupric  nitrate  or  carbonate,  both 
compounds  being  decomposed  with  formation  of  the  oxide ;  finally, 
it  may  be  made  by  adding  sodium  or  potassium  hydroxide  to  the 
solution  of  a  cupric  salt,  when  a  bulky,  pale-blue  precipitate  of  cupric 
hydroxide,  Cu(OH)2,  is  formed,  which,  upon  boiling,  is  decomposed  into 
water  and  cupric  oxide,  a  heavy  dark-brown  powder  (Plate  III.,  2) : 

CuSO,  +  2KOH  ==  K2SO4  +  Cu(OH)2; 
Cu(OH)2  =  H2O     +  CuO. 

Cuprous  oxide,  Cu2O  ( Red  oxide  or  suboxide  of  copper).  When 
cupric  oxide  is  heated  with  metallic  copper,  charcoal,  or  organic 
matter,  the  cupric  oxide  is  decomposed,  and  cuprous  oxide  is  formed. 
(Excess  of  carbon  or  organic  matter  reduces  the  oxide  to  metallic 

copper.) 

CuO  +  Cu  =  Cu2O; 
2CuO  +  C     =  Cu20  -f  CO. 


LEAD— COPPER— BISMUTH.  189 

Some  organic  substances,  especially  grape-sugar,  decompose  alkaline 
solutions  of  cupric  sulphate  with  precipitation  of  cuprous  oxide,  which 
is  a  red,  insoluble  powder. 

Cupric  sulphate,  Cupri  sulphas,  CuSO4.5H2O  =  249.2  (Sulphite 
of  copper,  Blue  vitriol,  Blue-stone).  This  is  the  most  important  com- 
pound of  copper.  It  is  manufactured  on  a  large  scale,  either  from 
copper  pyrites,  or  by  dissolving  cupric  oxide  in  sulphuric  acid, 
evaporating  and  crystallizing  the  solution  : 

CuO  +  H2SO4  =  CuSO,  -f  H2O. 

Cupric  sulphate  forms  large,  transparent,  deep-blue  crystals,  which 
are  easily  soluble  in  water,  and  have  a  nauseous,  metallic  taste.  By 
heating  it  to  about  200°  C.  (392°  F.)  all  water  of  crystallization  is 
expelled,  and  the  anhydrous  cupric  sulphate  formed,  which  is  a  white 
powder.  By  further  heating  this  is  decomposed,  sulphuric  and 
sulphurous  oxides  are  evolved,  and  cupric  oxide  is  left. 

Experiment  32.  Boil  about  5  grammes  of  fine  copper  wire  with  15  c.c.  of 
concentrated  sulphuric  acid  until  the  action  ceases  and  most  of  the  copper 
is  dissolved.  Dilute  with  about  15  c.c.  of  hot  water,  filter,  and  set  aside  for 
crystallization.  State  the  exact  quantities  of  copper  and  H2SO4  required  to 
make  100  pounds  of  crystallized  cupric  sulphate. 

Cupric  carbonate  is  obtained  by  the  addition  of  sodium  carbonate 
to  solution  of  cupric  sulphate,  when  a  bluish-green  precipitate  is 
formed,  which  is  cupric  carbonate  with  hydroxide  (Plate  III.,  4);  by 
dissolving  this  in  the  various  acids,  the  different  cupric  salts  are 
obtained. 

Ammonio-copper  compounds.  A  number  of  compounds  are 
known  which  are  either  double  salts  of  ammonia  and  copper,  or  are 
derived  from  ammonium  salts  and  contain  copper.  Thus,  cupric 
chloride  forms  with  ammonia  the  compounds :  CuCl2(NH3)2,  CuCl2 
(NH3)4,  and  CuCl2(NH3)6.  Cupric  sulphate  forms  in  like  manner, 
cupric-  diammonium  sulphate,  CuSO4(NH3)2,  and  cupric  tetrammo- 
nium  sulphate,  CuSO4(NH3)4,  which  is  a  deep  azure-blue  compound 
taking  up  one  molecule  of  water  during  crystallization. 

It  is  this  formation  of  soluble  ammonio-copper  compounds  which 
causes  the  deep  blue  color  in  solutions  of  cupric  salts  on  the  addition 
of  ammonia  water. 

Poisonous  properties  and  antidotes.  The  use  of  copper  for  culinary  vessels 
is  frequently  the  cause  of  poisoning  by  this  metal.  A  perfectly  clean  surface  of 


190  METALS  AND  THEIR  COMBINATIONS. 

metallic  copper  is  not  affected  by  any  of  the  substances  used  in  the  preparation 
of  food,  but  as  the  metal  is  very  apt  to  become  covered  with  a  film  of  oxide 
when  exposed  to  the  air,  and  as  the  oxide  is  easily  dissolved  by  the  combined 
action  of  water,  carbonic  or  other  acids,  such  as  are  found  in  vinegar,  the  juice 
of  fruits,  or  rancid  fats,  the  use  of  copper  for  culinary  vessels  is  always 
dangerous.  Actual  adulterations  of  food  with  compounds  of  copper  have  been 
detected. 

In  cases  of  poisoning  by  copper  the  stomach-pump  should  be  used,  vomiting 
induced,  and  albumen  (white  of  egg)  administered,  which  forms  an  insoluble 
compound  with  copper.  Reduced  iron,  or  a  very  dilute  solution  of  potassium 
ferrocyanide,  may  be  of  use  as  antidotes. 


Analytical  reactions. 
(Cupric  sulphate,  CuSO4,  may  be  used.) 

1.  Add  to  solution  of  copper,  hydrogen  sulphide  or  ammonium  sul- 
phide :  a  black  precipitate  of  cupric  sulphide  is  formed.  (Plate  III.,  1): 

CuSO4  -f  H2S  =  H2SO4  +  CuS. 

2.  Add  sodium  or  potassium  hydroxide :  a  bluish  precipitate  of 
cupric  hydroxide,  Cu(OH)2,  is  formed  which  is  converted  into  dark- 
brown  cupric  oxide,  CuO,  by  boiling.     (See  equation  above.)    (Plate 
III.,  2.) 

3.  Add   ammonium    hydroxide :    a  bluish  precipitate  of   cupric 
hydroxide  is  formed  which   readily  dissolves  in   an   excess  of  the 
reagent,  forming  a  deep  azure-blue  solution  containing  an  ammonio- 
copper  compound.     (See  explanation  above.)     (Plate  III.,  3.) 

4.  Add   potassium   ferrocyanide :    a   reddish-brown   precipitate  of 
cupric  ferrocyanide,  Cu2Fe(CN)6,  is  obtained.     (Plate  III.,  5.) 

5.  Add  solution  of  arsenous   acid  and   carefully   neutralize  with 
sodium  hydroxide  :  green  cupric  arsenite  is  precipitated.  (Plate  V.,  2.) 

6.  Add  sodium  or  potassium   carbonate :  green  cupric  carbonate 
with  hydroxide  is  precipitated.     (Plate  III.,  4.) 

7.  Immerse  a  piece  of  iron,  or  steel,  showing  a  bright  surface,  in 
an  acidified  solution  of  copper :  the  latter  is  precipitated  upon  the 
iron,  an  equivalent  amount  of  iron  passing  into  solution : 

CuS04  +  Fe  =  FeS04  +  Cu. 

8.  Most  compounds  of  copper  color  the  flame  green,  cupric  chloride 
blue. 

9.  Cupric  compounds  give  a  blue,  cuprous  compounds  a  red  borax 
bead. 

10.  Cupric  salts  (when  not  anhydrous)  have  mostly  a  blue  or  green 


PLATE    III. 


COPPER.      LEAD.       BISMUTH. 


Cupric  sulphide  or  lead  sul- 
phide, precipitated  from  solutions  of 
copper  or  lead  by  hydrogen  sulphide. 


Cupric  hydroxide  passing  into 
cupric  oxide.  Cupric  solutions  pre- 
cipitated by  potassium  hydroxide  and 
boiling. 


Cupric    solutions    treated  with 
ammonia  water. 


Cupric  carbonate,  precipitated 
from  cupric  solutions  by  sodium  car- 
bonate. 


Cupric  ferrocyaiiide,  precipita- 
ted from  cupric  solutions  by  potassium 
ferrocyanide. 


Lead    iodide,    precipitated    from 
lead  solutions  by  soluble  iodides. 


Lead  solutions  with  soluble  chlo- 
rides, sulphates  or  carbonates.  Bis- 
muth solutions  with  alkali  hydrox- 
ides or  carbonates. 


Bismuth  sulphide,  precipitated 
from  bismuth  solutions  by  hydrogen 
sulphide. 


LEAD— COPPER-BISMUTH.  191 

color:    sulphate,   nitrate,   chloride,   and  the  ammonio-copper  com- 
pounds are  soluble,  most  other  compounds  are  insoluble. 

Bismuth,  Bim  =  2O8.9.  Found  in  nature  chiefly  in  the  metallic 
state,  disseminated,  in  veins,  through  various  rocks.  The  extraction 
of  the  metal  is  a  mere  mechanical  process,  the  earthy  matter  contain- 
ing it  being  heated  in  iron  cylinders,  and  the  melted  bismuth  collected 
in  suitable  receivers. 

Bismuth  is  grayish-white,  with  a  pinkish  tinge,  very  brittle,  gen- 
erally showing  a  distinct  crystalline  structure.  Occasionally  it  is 
used  in  alloys  and  in  the  manufacture  of  a  few  medicinal  prepara- 
tions. 

Bismuth  is  trivalent,  as  shown  in  the  chloride,  BiCl3,  or  oxide, 
Bi2O3.  A  characteristic  property  of  this  metal  is  decomposition  of 
the  concentrated  solution  of  any  of  its  normal  salts  by  the  addition 
of  much  water,  with  the  formation  and  precipitation  of  so-called 
oxysalts  or  subsalts  of  bismuth,  while  some  bismuth  with  a  large 
quantity  of  acid  remains  in  solution. 

The  true  constitution  of  these  subsalts  is  as  yet  doubtful,  but  a 
comparison  of  them  has  led  to  the  assumption  of  a  radical  Bismuihyl, 
BiO,  which  behaves  like  an  atom  of  a  univalent  metal. 

The  relation  between  the  normal  or  bismuth  salts,  and  the  subsalts 
or  bismuthyl  salts,  will  be  shown  by  the  composition  of  the  following 
compounds : 

Bismuth  chloride,  BiCl3.  Bismuthyl  chloride,  (BiO)Cl. 

"        bromide,  BiBr3.  "          bromide,  (BiO)Br. 

"        iodide,  BiI3.  •'          iodide,  (BiO)I. 

nitrate,  Bi(NO3)3.  «          nitrate,  (BiO)NO3. 

"        sulphate,  Bi2(SO4)3.  "          sulphate,  (BiO)2SO4. 

«        carbonate,  Bi2(CO3)3  1  «          carbonate,  (BiO)2CO3. 

not  known.  ) 

Bismuthyl  nitrate,  Bismuth  subnitrate,  Bismuth!  subnitras, 
BiONO3.H2O?  (Oxynitrate  of  bismuth).  By  dissolving  metallic  bis- 
muth in  nitric  acid,  a  solution  of  bismuth  nitrate  is  obtained,  nitrogen 
dioxide  escaping : 

Bi  +  4HNO3  =  Bi(NO3)3  +  NO  +  2H2O. 

Upon  evaporation  of  the  solution,  colorless  crystals  of  bismuth 
nitrate,  Bi(NO3)35H2O,  are  obtained. 

If,  however,  the  solution  (or  the  dissolved  crystals)  be  poured  into 
a  large  quantity  of  water,  the  salt  is  decomposed  with  the  formation 


192  METALS  AND  THEIR  COMBINATIONS. 

of  bismuthyl  nitrate  and  nitric  acid,  which  latter  keeps  in  solution 
some  bismuth  : 

Bi(N03)3  +  2H20  =  BiON03.H20  +  2HNO3 

Subnitrate  of  bismuth  is  a  heavy,  white,  tasteless  powder,  almost 
insoluble  in  water,  soluble  in  most  acids. 

Experiment  33.  Dissolve  by  the  aid  of  heat  about  1  gramme  of  metallic  bis- 
muth in  a  mixture  of  2  c.c.  of  nitric  acid  and  1  c.c.  of  water.  Evaporate  the 
clear  solution  to  about  one-half  its  volume,  in  order  to  remove  excess  of  acid, 
and  pour  this  solution  of  normal  bismuth  nitrate  into  100  c.c.  of  water.  Col- 
lect the  precipitate  of  bismuthyl  nitrate  on  a  filter,  wash  and  dry  it.  Prove 
the  presence  of  bismuth  in  the  filtrate  by  tests  mentioned  below. 

Bismuthyl  carbonate,  Bismuth  subcarbonate,  Bismuth!  sub- 
carbonas,  (BiO)8CO3.H2O  (?)  (Oxy carbonate  of  bismuth,  Pearl-white). 
Made  by  adding  sodium  carbonate  to  solution  of  bismuth  nitrate, 
when  the  subcarbonate  is  precipitated,  some  carbon  dioxide  escaping: 

2[Bi(NO3)3]  -f  3Na2CO3  +  H2O  =  6NaNO3  +  2CO2  +  (BiO)2CO3.H2O. 

A  v/hite,  or  pale  yellowish-white  powder,  resembling  the  subnitrate. 
It  readily  loses  water  and  carbon  dioxide  on  heating,  when  the  yellow 
oxide,  Bi2O3,  is  left. 

Bismuthyl  iodide,  Bismuth  subiodide,  BiOI,  may  be  obtained 
by  adding  solution  of  hydriodic  acid  to  freshly  precipitated  bismuth 

oxide  : 

Bi2O3  +  2HI  =  2BiOI  +  H20. 

A  better  method  for  making  the  compound  is  to  pour  gradually  a 
solution,  made  by  dissolving  95  grammes  of  crystallized  normal  bis- 
muth nitrate  in  125  c.c.  of  glacial  acetic  acid,  into  a  solution  of  40 
grammes  of  potassium  iodide,  and  55  grammes  of  sodium  acetate  in 
2500  c.c.  of  water.  The  precipitate,  which  has  a  brick-red  color,  is 
well  washed  and  dried  at  100°  C.  (212°  F.).  The  decomposition  is 

this : 

2[Bi(N03)3]  +  2H20       +  2KI        +  4NaC2H3O2  = 
2(BiOI)          +  4NaNO3  -f  2KNO3  +  4C2H4O2- 

Analytical  reactions. 
(Bismuth  nitrate,  Bi(NO3)3,  or  bismuth  chloride,  BiCl3,  may  be  used.) 

1.  Add  to  solution  of  bismuth,  hydrogen  sulphide  or  ammonium 
sulphide :  a  dark-brown  (almost  black)  precipitate  of  bismuth  sul- 
phide, Bi2S3,  is  produced  (Plate  III.,  8): 

2BiCl3  +  3H2S  =  6HC1  -f  Bi2S3. 


SILVER— MERCURY.  193 

2.  Pour  a  concentrated  solution  of  bismuth  into  water:  a  white 
precipitate  of  a  bismuthyl  salt  is  formed.     (See  explanation  above.) 

3.  Add  to  bismuth  solution  ammonium  or  sodium  hydroxide,  or 
carbonate :  a  white  precipitate  of  bismuth  hydroxide,  Bi(OH)3,  or  of 
bismuthyl  carbonate  is  produced.     (See  explanation  above.) 

4.  Potassium  iodide  precipitates  brown  bismuth  iodide,  BiI3,  solu- 
ble in  excess  of  the  reagent. 

5.  Potassium  dichromate  precipitates  yellow  bismuthyl  dichromate, 
(BiO)2Cr2O7. 

6.  A  small   quantity  of  bismuth   or  of  any  bismuth  compound, 
mixed  with  sulphur  and  potassium  iodide,  and  heated  upon  charcoal 
before  the  blow-pipe,  forms  a  scarlet-red  incrustation  of  bismuthyl 
iodide,  BiOI. 

29.    SILVER— MERCURY. 

Silver,  Ag  =  1O7.7  (Argentum).  This  metal  is  found  sometimes 
in  the  metallic  state,  but  generally  as  a  sulphide,  which  is  nearly 
always  in  combination  with  large  quantities  of  lead  sulphide,  such 
ore  being  known  as  argentiferous  galena.  The  lead  manufactured 
from  this  ore  contains  the  silver,  and  is  separated  from  it  by  roasting 
the  alloy  in  a  current  of  air,  whereby  lead  is  oxidized  and  converted 
into  litharge,  while  pure  silver  is  left. 

Silver  is  the  whitest  of  all  metals,  and  takes  the  highest  polish ; 
it  is  the  best  conductor  of  heat  and  electricity,  and  melts  at  about 
1000°  C.  (1832°  F.) ;  it  is  univalent,  and  forms  but  one  series  of  salts; 
it  is  not  aifected  by  the  oxygen  of  the  air  at  any  temperature,  but  is 
readily  acted  upon  by  traces  of  hydrosulphuric  acid,  which  forms  a 
black  film  of  sulphide  upon  the  surface  of  metallic  silver.  Hydro- 
chloric acid  scarcely  acts  on  silver,  nitric  and  sulphuric  acids  dis- 
solve it. 


QUESTIONS.— 271.  What  are  the  properties  of  lead  and  from  what  ore  is  it 
obtained?  272.  What  is  litharge,  and  how  does  it  differ  from  red  lead?  273. 
Give  the  composition  of  nitrate,  carbonate,  and  iodide  of  lead ;  how  are  they 
made?  274.  State  the  analytical  reactions  for  lead.  275.  How  is  copper 
found  in  nature?  276.  How  many  oxides  of  copper  are  known;  what  is  their 
composition,  and  under  what  conditions  are  they  formed  ?  277.  What  is  "  blue 
vitriol ;  "  how  is  it  made,  and  what  are  its  properties  ?  278.  How  does  ammo- 
nium hydroxide  act  on  cupric  solutions  ?  279.  Mention  tests  for  copper.  280. 
What  is  the  composition  of  subnitrate  and  subcarbonate  of  bismuth ;  how  are 
they  made  from  metallic  bismuth,  and  what  explanation  is  given  in  regard  to 
their  constitution  ? 

13 


194  METALS  AND  THEIR  COMBINATIONS. 

While  many  of  the  non-metallic  elements  have  long  been  known  to  exist  in 
allotropic  forms,  none  of  the  metals  had  been  obtained  in  such  a  condition 
until  quite  recently,  when  it  was  shown  that  silver  is  capable  of  assuming  a 
number  of  allotropic  modifications.  These  are  obtained  chiefly  by  precipi- 
tating silver  from  solutions  by  different  reducing  agents.  While  normal  silver 
is  white,  the  allotropic  forms  have  distinct  colors — blue,  bluish-green,  red,  pur- 
ple, yellow — and  differ  also  in  many  other  respects.  Thus  they  are  converted 
into  silver  chloride  by  highly  diluted  hydrochloric  acid,  which  does  not  act  on 
common  silver;  they  are  soluble  in  ammonia  water,  and  act  as  reducing  agents 
upon  a  number  of  substances,  such  as  permanganates,  ferricyanides,  etc.  Allo- 
tropic silver  can  be  converted  into  the  common  form  by  different  forms  of 
energy — for  instance,  by  heat,  electricity,  and  the  action  of  strong  acids. 

Silver  is  too  soft  for  use  as  coin  or  silverware,  and,  therefore,  is 
alloyed  with  from  5  to  25  per  cent,  of  copper,  which  causes  it  to  be- 
come harder,  and  consequently  gives  it  more  resistance  to  the  wear 
and  tear  by  friction. 

Pure  silver  may  be  obtained  by  dissolving  silver  coin  in  nitric  acid, 
when  a  blue  solution,  containing  the  nitrates  of  copper  and  silver,  is 
formed.  By  the  addition  of  sodium  chloride  to  the  solution  a  white 
curdy  precipitate  of  silver  chloride,  AgCl,  forms,  while  cupric  nitrate 
remains  in  solution.  The  silver  chloride  is  washed,  dried,  mixed 
with  sodium  carbonate,  and  heated  in  a  crucible,  when  sodium  chlo- 
ride is  formed,  carbon  dioxide  escapes,  and  a  button  of  silver  is  found 
at  the  bottom  of  the  crucible : 

2AgCl  +  Na,C08  =  2NaCl  +  CO2  +  2Ag  +  O. 

Experiment  34.  Dissolve  a  small  silver  coin  in  nitric  acid,  dilute  with  water, 
and  precipitate  the  clear  liquid  with  an  excess  of  solution  of  sodium  chloride. 
The  washed  precipitate  of  silver  chloride  may  be  treated  with  sodium  carbon- 
ate, as  stated  above,  or  may  be  converted  into  metallic  silver  by  the  following 
method :  Place  the  dry  chloride  in  a  small  porcelain  crucible  and  apply  a 
gentle  heat  until  the  chloride  has  fused ;  when  cold,  place  a  piece  of  sheet 
zinc  upon  the  chloride,  cover  with  water,  to  which  a  few  drops  of  sulphuric 
acid  have  been  added,  and  set  aside  for  a  day,  when  the  silver  chloride  will  be 
found  to  have  been  decomposed  with  liberation  of  metallic  silver  and  forma- 
tion of  zinc  chloride  : 

2AgCl  +  Zn  =  ZnCl2  +  2Ag. 

Wash  the  spongy  silver  with  dilute  sulphuric  acid  and  then  with  water. 
Use  this  silver  for  making  silver  nitrate  by  dissolving  it  in  nitric  acid,  and 
evaporation  of  the  solution  to  dryness.  Use  this  solution  for  silver  reactions. 

Silver  nitrate,  Argenti  nitras,  Ag-NO3  =  169.7.  Pure  silver  is 
dissolved  in  nitric  acid  : 

3Ag  +  4HN03  =  NO  +  2H2O  +  3AgNO8. 


SILVER— MERCURY.  195 

The  solution  is  evaporated  to  dryness  with  the  view  of  expelling  all 
free  acid,  the  dry  mass  dissolved  in  hot  water  and  crystallized. 

If  the  silver  used  should  contain  copper,  the  latter  may  be  elimin- 
ated from  the  mixture  of  silver  and  cupric  nitrate  by  evaporating  to 
dryness  and  fusing,  when  the  latter  salt  is  decomposed,  insoluble 
cupric  oxide  being  formed.  The  fused  mass  is  dissolved  in  water, 
filtered,  and  again  evaporated  for  crystallization. 

When  silver  nitrate,  after  the  addition  of  4  per  cent,  of  hydro- 
chloric acid,  is  fused  and  poured  into  suitable  moulds  it  yields  the 
wrhite  cylindrical  sticks  which  are  known  as  moulded  silver  nitrate, 
caustic,  lunar  caustic,  or  lapis  infernalis. 

When  fused  with  twice  its  weight  of  potassium  nitrate  and  formed 
into  similar  rods,  it  forms  the  diluted  silver  nitrate  (mitigated  caustic) 
of  the  U.  S.  P. 

Silver  nitrate  forms  colorless,  transparent,  tabular,  rhombic  crys- 
tals, or,  when  fused,  a  white,  hard  substance ;  it  is  soluble  in  less 
than  its  own  weight  of  water,  the  solution  having  a  neutral  reaction. 
Exposed  to  the  light,  especially  in  the  presence  of  organic  matter, 
silver  nitrate  blackens  in  consequence  of  decomposition ;  when 
brought  in  contact  with  animal  matter,  it  is  readily  decomposed  into 
free  nitric  acid  and  metallic  silver,  which  produces  the  characteristic 
black  stain ;  it  is  this  decomposition,  and  the  action  of  the  free  nitric 
acid,  to  which  the  strongly  caustic  properties  of  silver  nitrate  are 
due. 

Nitrate  of  silver  is  used  largely  in  photography,  and  also  in  the 
manufacture  of  various  kinds  of  indelible  inks  and  hair-dyes. 

Silver  oxide,  Argenti  oxidum,  Ag"2O  =  231.4.  Made  by  the 
addition  of  an  alkali  hydroxide  to  silver  nitrate  : 

2AgN03  +  2KOH  =  2KNO3  +  H2O  +  Ag2O. 

A  dark-brown,  almost  black  powder,  but  very  sparingly  soluble 
in  water,  imparting  to  the  solution  a  weak  alkaline  reaction.  It  is  a 
strong  base,  and  easily  decomposed  into  silver  and  oxygen. 

Silver  iodide,  Argenti  iodidum,  Ag-I  —  234.3.  Made  by  the 
addition  of  potassium  iodide  to  silver  nitrate  : 

AgNO3  +  KI  =  KNO3  -f  Agl. 

A  heavy,  amorphous,  light  yellowish  powder,  insoluble  in  water, 
and  but  slightly  soluble  in  ammonium  hydroxide. 

Antidotes.    Sodium  chloride,  white  of  egg,  or  milk,  followed  by  an  emetic. 


196  METALS  AND  THEIR  COMBINATIONS. 

Analytical  reactions. 

(Silver  nitrate,  AgNO3,  may  be  used.) 

1.  Add  to  solution  of  a  silver  salt,  hydrogen  sulphide  or  ammonium 
sulphide  :  a  dark-brown  precipitate  of  silver  sulphide  is  produced  : 

2AgNO3  -f  H2S  =  2HNO3  +  Ag2S. 

2.  Add  hydrochloric  acid,  or  any  soluble  chloride  :  a  white,  curdy 
precipitate  of  silver  chloride  is  produced,  which  is  insoluble  in  dilute 
acids,  but  soluble  in  ammonium  hydroxide  and  in  potassium  cyanide. 

AgNO3  +  NaCl  =  NaN03  +  AgCl. 

3.  Add  potassium  chromate  or  dichromate  :  a  red  precipitate  of 
silver  chromate,  Ag2CrO4,  is  formed  (Plate  II.,  7). 

4.  Add  sodium   phosphate  :   a  pale-yellow   precipitate  of  silver 
phosphate,  Ag3PO4,  is  formed,  which  is  soluble  in  ammonia  and  in 
nitric  acid. 

5.  Alkali  hydroxides  precipitate  dark-brown  silver  oxide,  soluble 
in  ammonia  water. 

6.  Potassium  iodide  or  bromide  gives  a  pale-yellow  precipitate. 
(See  above.) 

7.  Metallic  copper,  zinc,  or  iron  precipitates  metallic  silver. 

Mercury,  Hydrargyrum,  Hg-  =  199.8  (Quicksilver}.  Mercury  is 
found  sometimes  in  small  globules  in  the  metallic  state,  but  generally 
as  mercuric  sulphide  or  cinnabar,  a  dark-red  mineral.  The  chief 
supply  was  formerly  obtained  from  Spain  and  Austria ;  now,  how- 
ever, large  quantities  are  obtained  from  California ;  it  is  also 
imported  from  Peru  and  Japan. 

Mercury  is  obtained  from  cinnabar  either  by  roasting  it,  whereby 
the  sulphur  is  converted  into  sulphur  dioxide,  or  by  heating  it  with 
lime,  which  combines  with  the  sulphur,  while  the  metal  volatilizes, 
and  is  condensed  by  passing  the  vapors  through  suitable  coolers. 

Mercury  is  the  only  metal  showing  the  liquid  state  at  the  ordinary 
temperature ;  it  solidifies  at  —40°  C.  (— 40d  F.),  and  boils  at  357°  C. 
(675°  F.) ;  but  is  slightly  volatile  at  all  temperatures  ;  it  is  almost 
silver- white,  and  has  a  bright  metallic  lustre  ;  its  specific  gravity  is 
13.56  at  15°  C.  (59°  F.). 

Mercury  is  peculiar  in  that  its  molecule  contains  but  one  atom,  at 
least  when  in  the  state  of  a  gas  ;  in  the  liquid  and  solid  states  it  may 
contain  two  atoms,  like  most  other  elements,  but  we  have  as  yet  no 
means  of  proving  this  fact. 


SILVER— MERCURY.  197 

Mercury  is  bivalent,  and  forms,  like  copper,  two  series  of  com- 
pounds, distinguished  as  mercuric  and  mercurous  compounds.  In 
the  former,  one  atom  of  mercury  exerts  its  bivalence,  as  in  HgO, 
HgCl2;  in  the  mercurous  compounds  two  atoms  of  mercury  exert 
the  same  valence,  as  in  Hg2O,  Hg2Cl2.  In  order  to  explain  this 
behavior  we  have  to  assume  that  of  the  four  points  of  attraction, 
represented  by  the  two  atoms  of  mercury,  two  are  required  to  hold 
together  or  unite  these  two  atoms,  so  as  to  leave  but  two  for  other 

elements. 

/Cl  Hg— Cl 

Hg< 

XC1  Hg— Cl 

Mercuric  chloride.  Mercurous  chloride. 

There  are  known,  however,  some  data  which  seem  to  contradict 
this  view  and  make  it  not  unlikely  that  the  composition  of  mercurous 
chloride  is  HgCl,  and  not  Hg2Cl2. 

Mercury  is  not  affected  by  the  oxygen  of  the  air,  nor  by  hydro- 
chloric acid,  while  chlorine,  bromine,  and  iodine  combine  with  it 
directly,  and  wrarm  sulphuric  and  nitric  acids  dissolve  it. 

Mercury  is  used  in  the  metallic  state  for  many  scientific  instruments 
(thermometer,  barometer,  etc.) ;  in  the  silvering  of  looking-glasses, 
which  is  effected  by  means  of  an  amalgam  of  tin  (amalgams  are  alloys 
in  which  mercury  is  one  of  the  constituents)  ;  for  manufacturing  from 
it  all  of  the  various  mercury  compounds,  and  those  official  prepara- 
tions in  which  mercury  exists  in  the  metallic  state. 

These  latter  preparations  are :  Mercury  with  chalk,  blue  mass  or 
blue  pill,  mercurial  ointment,  and  mercurial  plaster.  Mercury  exists  in 
a  metallic,  but  highly  subdivided  state  in  these  preparations,  which 
are  made  by  intimately  mixing  (triturating)  metallic  mercury  with 
the  different  substances  used  (viz.,  chalk,  pill-mass,  fat,  lead-plaster). 
It  is  most  probable  that  the  action  of  these  agents  upon  the  animal 
system  is  chiefly  due  to  the  conversion  of  small  quantities  of  mercury 
into  mercurous  oxide,  which,  in  contact  with  the  acids  of  the  gastric 
juice  or  with  perspiration,  are  converted  into  soluble  compounds 
capable  of  being  absorbed. 

Mercurous  oxide,  Hg-2O  (Black  oxide  or  suboxide  of  mercury). 
An  almost  black,  insoluble  powder,  made  by  adding  an  alkaline 
hydroxide  to  a  solution  of  mercurous  nitrate : 

Hg2(NO3)2  +  2KOH  =  2KN03  +  H2O  +  Hg2O. 

A  similar  decomposition  takes  place  when  alkaline  hydroxides  are 
added  to  insoluble  mercurous  chloride.  A  mixture  of  lime-water  and 


198  METALS  AND  THEIR  COMBINATIONS. 

mercurous  chloride  (calomel)  is  known  as  black-wash  ;  when  the  two 
substances  are  mixed,  calomel  is  converted  into  mercurous  oxide, 
while  calcium  chloride  is  formed  : 

Hg2Cl2  +  Ca(OH)2  =  CaCl2  -f  H2O  +  Hg2O. 

Mercuric  oxide,  HgO  =  215.8.  There  are  two  mercuric  oxides 
which  are  official  ;  they  do  not  differ  in  their  chemical  composition, 
but  in  their  molecular  structure. 

The  yellow  mercuric  oxide,  Hydrargyri  oxidum  flavum,  is  made 
by  pouring  a  solution  of  mercuric  chloride  into  a  solution  of  sodium 
hydroxide,  when  an  orange-yellow,  heavy  precipitate  is  produced, 
which  is  washed  and  dried  at  a  temperature  not  exceeding  30°  C. 
(86°  F.)  (Plate  IV.,  3): 

HgCl2  +  2NaOH  =  HgO  +  2NaCl  +  H2O. 

The  red  mercuric  oxide,  Hydrargyri  oxidum  rubrum,  or  red  pre- 
cipitate, is  made  by  heating  mercuric  nitrate,  either  by  itself  or  after 
it  has  been  intimately  mixed  with  an  amount  of  metallic  mercury 
equal  to  the  mercury  in  the  nitrate  used  (Plate  IV.,  4).  In  the 
first  case,  nitrous  fumes  and  oxygen  are  given  off,  mercuric  oxide 

remaining  : 

Hg(N03)2  =  HgO  -f  2N02  +  O. 

In  the  other  case,  no  oxygen  is  evolved  : 

Hg(N03)s  +  Hg  =  2HgO  +  2N02. 

The  red  oxide  of  mercury  differs  from  the  yellow  oxide  in  being 
more  compact,  and  of  a  crystalline  structure  ;  while  the  yellow  oxide 
is  in  a  more  finely  divided  state,  and  consequently  acts  more  energeti- 
cally when  used  in  medicine.  Yellow  oxide,  when  digested  on  a 
water-bath  with  a  strong  solution  of  oxalic  acid,  is  converted  into 
white  mercuric  oxalate  within  fifteen  minutes,  while  red  oxide  is  not 
acted  upon  by  oxalic  acid  under  the  same  conditions. 

When  mercuric  chloride  is  added  to  lime-water,  a  mixture  is 
formed  holding  in  suspension  yellow  mercuric  oxide;  this  mixture 
is  known  as  yellow-wash. 

Experiment  35.  Heat  some  mercuric  nitrate  in  a  porcelain  dish,  placed  in  a 
fume  chamber,  until  red  fumes  no  longer  escape.  The  remaining  red  powder 
is  mercuric  oxide,  which,  by  further  heating,  may  be  decomposed  into  its  ele- 
ments. 


Mercurous  chloride,  Hydrargyrum  chloridum    mite, 
=  47O.4  (Calomel,   Mild  chloride  of  mercury,  Subchloride  or  proto- 
chloride  of  mercury).      Mercurous  chloride,  like  mercurous  oxide, 


SILVER— MERCURY.  199 

may  be  made  by  different  processes,  but  the  article  used  medicinally 
is  the  one  obtained  (except  it  be  otherwise  stated)  by  sublimation 
and  the  rapid  condensation  of  the  vapor  in  the  form  of  powder. 
It  is  made  either  by  subliming  a  mixture  of  mercuric  chloride 

and  mercury: 

HgCl2  +  Hg  =  Hg2Cl2. 

or  by  thoroughly  mixing  with  mercuric  sulphate  a  quantity  of  mer- 
cury equal  to  that  contained  in  the  sulphate ;  by  this  operation  mer- 
curous sulphate  is  obtained,  which  is  mixed  with  sodium  chloride, 
and  sublimed  from  a  suitable  apparatus  into  a  large  chamber,  so  that 
the  sublimate  may  fall  in  powder  to  the  floor : 

HgS04  +  Hg  +  2NaCl  =  Na2SO4  +  Hg2Cl2. 

Precipitated  calomel,  being  in  a  finer  state  of  subdivision,  acts 
more  energetically  when  used  medicinally.  It  is  obtained  by  pre- 
cipitation of  a  soluble  mercurous  salt  by  any  soluble  chloride: 

Hg2(NO3)2  +  2NaCl  =  2NaNO3  +  Hg2Cl2. 

Mercurous  chloride,  made  by  either  process,  generally  contains 
traces  of  mercuric  chloride,  and  should,  therefore,  be  washed  with 
hot  water  until  the  washings  are  no  longer  acted  upon  by  ammonium 
sulphide  or  silver  nitrate. 

Mercurous  chloride  is  a  white,  impalpable,  tasteless  powder,  in- 
soluble in  water  and  alcohol ;  it  volatilizes  without  fusing  previously;' 
when  given  internally,  it  should  not  be  mixed  with  either  mineral 
acids,  alkali  bromides,  iodides,  hydroxides,  or  carbonates,  except  the 
action  of  the  decomposition  products  be  desired. 

Mercuric  chloride,  Hydrargyri  chloridum  corrosivum,  HgCl2 
=  27O.6  (Corrosive  chloride  of  mercury,  Corrosive  sublimate,  Per  chlo- 
ride or  bichloride  of  mercury).  Made  by  thoroughly  mixing  mercuric 
sulphate  with  sodium  chloride,  and  subliming  the  mixture,  when 
mercuric  chloride  is  formed,  and  passes  off  in  white  fumes  which  are 
condensed  in  the  cooler  part  of  the  apparatus,  while  sodium  sulphate 

is  left: 

HgSO4  +  2NaCl  =  Na2SO4  +  HgCl2. 

Mercuric  chloride  is  a  heavy,  white  powder,  or  occurs  in  heavy, 
colorless,  rhombic  crystals  or  crystalline  masses;  it  is  soluble  in  16 
parts  of  cold  and  2  parts  of  boiling  water,  and  in  about  3  parts  of 
alcohol,  in  4  parts  of  ether,  and  in  about  14  parts  of  glycerin;  when 
heated,  it  fuses  and  is  volatilized ;  it  has  an  acrid,  metallic  taste,  an 
acid  reaction,  and  strongly  poisonous  and  antiseptic  properties. 


200  METALS  AND  THEIR  COMBINATIONS. 

Mercurous  iodide,  Hydrargyri  iodidum  flavum,  Hg2I2=  652.6 
(  Yellow  iodide,  green  iodide,  or  protiodide  of  mercury).  Both  iodides 
of  mercury  may  be  obtained  either  by  rubbing  together  mercury  and 
iodine  in  the  proportions  represented  by  the  respective  atomic  weights, 
or  by  precipitation  of  soluble  mercurous  or  mercuric  salts  by  potas- 
sium iodide. 

According  to  the  U.  S.  P.,  mercurous  iodide  is  made  by  the  pre- 
cipitation of  a  4  per  cent,  solution  of  mercurous  nitrate,  to  which  1 
per  cent,  of  nitric  acid  has  been  added,  by  a  2.4  per  cent,  solution  of 
potassium  iodide: 

Hg2(N03)2  +  2KI  =  2KN03  +  Hg2I2. 

The  precipitate  is  collected  on  a  filter,  well  washed  with  water  and 
alcohol,  and  dried  between  paper  at  a  temperature  not  exceeding 
40°  C.  (104°  F.).  During  the  whole  operation  light  should  be  ex- 
cluded as  much  as  possible,  as  it  decomposes  the  compound. 

Mercurous  iodide  is  a  yellow,  tasteless  powder,  almost  insoluble  in 
water.  It  is  easily  decomposed  into  mercuric  iodide  and  mercury, 
becoming  darker  and  assuming  a  greenish-yellow  tint  (Plate 
IV.,  5.) 

Mercuric  iodide,  Hydrargyri  iodidum  rubrum,  HgI2—  452.8 
(Hed  iodide  or  biniodide  of  mercury).  Made  by  mixing  solutions  of 
potassium  iodide  and  mercuric  chloride,  when  a  pale-yellow  precipi- 
tate is  formed,  turning  red  immediately  (Plate  IV.,  6) : 

HgCl2  +  2KI  =  2KC1  +  HgI2. 

Mercuric  iodide  is  soluble  both  in  solution  of  potassium  iodide  and 
mercuric  chloride,  for  which  reason  an  excess  of  either  substance  will 
cause  a  loss  of  the  salt  when  prepared.  It  is  a  scarlet-red,  tasteless 
powder,  almost  insoluble  in  water  and  but  slightly  soluble  in  alcohol ; 
on  heating  or  subliming  it  turns  yellow  in  consequence  of  a  molecular 
change  which  takes  place ;  on  cooling,  and,  more  quickly,  on  pressing 
or  rubbing  the  yellow  powder,  it  reassumes  the  original  condition 
and  the  red  color. 

Mercuric  sulphate,  Hg-SO4.  When  mercury  is  heated  with  strong 
sulphuric  acid  (the  presence  of  nitric  acid  facilitates  the  formation) 
chemical  action  takes  place  between  the  two  substances,  sulphur 
dioxide  being  liberated  and  mercuric  sulphate  formed,  which  is  ob- 
tained as  a  heavy,  white,  crystalline  powder : 

Hg  +  2H2SO4  =  HgS04  -j-  2H2O  +  SO2. 


SILVER-MERCURY.  201 

Yellow  mercuric  subsulphate,  Hydrargyri  subsulphas  flavus, 
HgrSO4.(HgO)2  =  727.4  (Basic  mercuric  sulphate,  Turpeth  mineral, 
Mercuric  oxy-sulphate).  When  mercuric  sulphate,  prepared  as  directed 
above,  is  thrown  into  boiling  water,  it  is  decomposed  into  an  acid 
salt  which  remains  in  solution,  and  a  basic  salt  which  is  precipitated. 
As  shown  by  its  composition,  HgSO4.(HgO)2,  it  may  be  looked  upon 
as  mercuric  sulphate  in  combination  with  mercuric  oxide.  It  is  a 
heavy,  lemon-yellow,  tasteless  powder,  almost  insoluble  in  water. 

Mercurous  sulphate,  Hg2SO4.  When  mercuric  sulphate  is  triturated 
with  a  sufficient  quantity  of  mercury,  direct  combination  takes  place, 
and  the  mercurous  salt  is  formed : 

HgS04  +  Hg  =  Hg2S04. 

Nitrates  of  mercury.  Mercurous  nitrate,  Hg2(NO3)2,  and  Mer- 
curic nitrate,  Hg(NO3)2,  may  both  be  obtained  as  white  salts  by  dis- 
solving mercury  in  nitric,  acid.  The  relative  quantities  of  the  two 
substances  present  determine  whether  mercurous  or  mercuric  nitrate 
be  formed.  If  mercury  is  present  in  excess  the  mercurous  salt,  if  nitric 
acid  is  present  in  excess  the  mercuric  salt,  is  formed,  the  latter  espe- 
cially on  heating.  Both  salts  are  white  and  soluble  in  water. 

Experiment  36.  Heat  gently  a  small  globule  (about  1  gramme)  of  mercury 
with  2  c.c.  of  nitric  acid  until  red  fumes  cease  to  escape.  If  some  of  the  mer- 
cury remains  undissolved,  the  solution  will  deposit  crystals  of  mercurous 
nitrate  on  cooling.  Use  some  of  the  solution,  after  being  diluted  with  much 
water,  for  mercurous  tests.  Use  another  portion  as  follows :  Heat  the  solution, 
or  some  of  the  crystals,  with  about  an  equal  weight  of  nitric  acid  until  no  more 
red  fumes  escape.  Add  to  a  few  drops  of  the  diluted  liquid  a  little  hydro- 
chloric acid,  which,  if  the  conversion  of  the  mercurous  into  mercuric  salt  has 
been  complete,  will  give  no  precipitate.  If,  however,  one  should  be  formed,  the 
solution  is  heated  with  more  nitric  acid  until  no  precipitate  is  formed  by  hydro- 
chloric acid,  when  the  solution  is  evaporated  and  set  aside  for  crystallization. 

The  respective  changes  may  be  represented  by  the  following  equations : 

6Hg  +  8HN03  =  3[Hg2(N03y  +  4H2O  +  2NO; 
3[Hg2(N03)2]  +  8HN03  =  6[Hg(NO8)a]    +  4H2O  +  2NO. 

Mercuric  sulphide,  Hg-S  =  231.8.  This  compound  has  been 
mentioned  as  the  chief  ore  of  mercury,  occurring  crystallized  as  cin- 
nabar, which  has  a  red  color  (Plate  IV.,  2).  The  same  compound 
may,  however,  be  obtained  by  passing  hydrosulphuric  acid  gas 
through  mercuric  solutions,  when  at  first  a  white  precipitate  is 
formed  (a  double  compound  of  the  sulphide  of  mercury  in  combina- 
tion with  the  mercuric  salt),  which  soon  turns  black  (Plate  IV.,  1): 

HgCl2  +  H2S  =  2HC1  +  HgS. 

The  black,  amorphous,  mercuric  sulphide  may  be  converted  into  the 
red,  crystallized  variety  by  sublimation,  and  is  then  the  preparation 


202 


METALS  AND  THEIR  COMBINATIONS. 


known  as  red  sulphide  of  mercury,  cinnabar,  or  vermilion.  It  forms 
brilliant  dark-red  crystalline  masses,  or  a  fine  bright  scarlet  powder, 
which  is  insoluble  in  water,  hydrochloric  or  nitric  acid,  but  soluble 
in  nitro-hydrochloric  acid. 

Mercuric  and  rnercurous  sulphides  may  be  made  also  by  triturating 
the  elements  mercury  and  sulphur  in  the  proper  proportions,  when 
they  combine  directly. 


Ammoniated  mercury,  Hydrargyrum  ammoniatum, 
=  251.2  (  White  precipitate.  Mercuric-ammonium  chloride).    This  com- 
pound is  made  by  pouring  solution  of  mercuric  chloride  into  water  of 
ammonia,  when  a  white  precipitate  falls,  which  is  washed  with  highly 
diluted  ammonia  water  and  dried  at  a  low  temperature  : 
HgCl2  +  2NH4OH  4=  NH2HgCl  +  NH4C1  +  2H2O. 

As  shown  by  the  composition  of  this  compound,  it  may  be  re- 
garded as  ammonium  chloride,  NH4C1,  in  which  two  atoms  of  hydro- 
gen have  been  replaced  by  one  atom  of  the  bivalent  mercury.  (There 
are  many  compounds  known  in  which  metallic  atoms  replace  hydrogen 
in  salts  of  ammonium  ;  the  ammonium  copper  compounds  belong  to 
this  group  of  substances.) 

Ammoniated  mercury  is  a  white,  tasteless,  insoluble  powder. 


Analytical  reactions. 


Mercurous  salts. 

(Mercurous  nitrate,  Hg2(No3)2  may 
be  used.) 


Mercuric  salts. 
(Mercuric  chloride,  HgCl2,  may 


1.  Hydrogen  sul- 
phide, or  ammo- 
nium sulphide. 


2.  Potassium  iodide 


3.  Potassium  or  so- 
dium hydroxide. 

4.  Ammonium   hy- 
droxide. 


5.  Potassium  or  so- 
dium carbonate. 

6.  Hydrochloric 
acid  or  soluble 
chlorides. 


Black  precipitate  of  mercuric 
sulphide,  with  mercury. 
Hff.(NOt),  +  H2S  = 
2HN03  +  HgS  +  Hg. 

Green  precipitate  of  mercurous 
iodide  (Plate  IV.,  7): 
Hg2(N03)2  +  2KI  = 
2KN03  +  Hg2I2. 
Dark -brown  precipitate  of  mer 
curous   oxide,    Hg2O   (Plate 
IV.,  5). 

Black  precipitate  of  mercurous 
ammonium  salt  is  formed. 
(The  insoluble  white  calomel 
is  converted  into  a  black 
powder.) 

Yellowish  precipitate  of  mer- 
curous carbonate,  which  is 
unstable. 

White  precipitate  of  mercurous 
chloride  is  produced : 

Hg2(N03)2-f2HCl  = 
2HN03  +  Hg2Cl2. 


Black  precipitate  of  mercuric 
sulphide.  (Precipitate  may  be 
white  or  gray,  with  an  insuffi- 
cient quantity  of  the  reagent.) 
(See  above  )  (Plate  IV.,  1.) 

Red  precipitate  of  mercuric 
iodide  (See  above.)  (Plate 
IV.,  6.) 

Yellow  precipitate  of  mercuric 

oxide      HgO.      (See  above.) 

(Plate  IV.,  3.) 
White  precipitate  of  a  mercuric 

ammonium    salt    is   formed. 

(See  explanation  above.) 


Brownish-red   precipitate  of 
basic   mercuric  carbonate. 
HgC03.3HgO. 

No  change 


IV. 


MERCURY.       SILVER. 


Mercuric  sulphide,  precipitated 
from  mercuric  solutions  by  hydrogen 
sulphide. 


Mercuric  sulphide,  Cinnabar. 


Yellow  mercuric  oxide,  precipi- 
tated from  mercuric  solutions  by  po- 
tassium hydroxide. 


Red  mercuric  oxide, obtained  by 
heating  mercuric  nitrate. 


Mercurous  oxide,  precipitated 
f  rom  mercurous  solutions  by  potassium 
hydroxide. 

Silver  sulphide,  precipitated  from 
silver  solutions  by  hydrogen  sulphide. 


Mercuric  iodide,  precipitated 
from  mercuric  solutions  by  alkali 
iodides. 


Mercurous  iodide,  precipitated 
from  mercurous  solutions  by  alkali 
iodides. 


Mercuric  solutions  with  ammo- 
nium hydroxide.  Mercurous  solu- 
tions with  soluble  chlorides.  Silver 
solution*  with  soluble  chlorides. 


SILVER-MERCURY.  203 

7.  Stannous  chloride  produces,  in  solutions  of  mercury,  a  white 
precipitate,  which  turns  dark-gray  on  heating  with  an  excess  of  the 
reagent.     The  reaction  is  due  to  the  strong  reducing  or  deoxidizing 
property  of  the  stannous  chloride,  which  itself  is.con  verted  into  stannic 
chloride,  while  the  mercury  salt  is  first  converted  into  a  mercurous 
salt  and  afterward  into  metallic  mercury  : 

2HgCl2    +  SnCL,  =  Hg2Cl2  +  SnCl4; 
Hg2Cl2  -f  SnCl2  =  2Hg       -f  SnCl4. 

8.  Dry  mercury  compounds,  when  mixed  with  sodium  carbonate 
and  potassium  cyanide,  and  heated  in  a  narrow  test-tube,  are  decom- 
posed with  liberation  of  metallic  mercury,  which  condenses  in  small 
globules  in  the  cooler  part  of  the  tube. 

9.  A  piece  of  bright  metallic  copper,  when  placed  in  a  slightly  acid 
mercury  solution  becomes  coated  with  a  dark  film  of  metallic  mer- 
cury, which  by  rubbing  becomes  bright  and  shining,  and  may  be 
volatilized  by  heat. 

10.  All  compounds  of  mercury  are  completely  volatilized  by  heat, 
either  with  or  without  decomposition. 

Antidotes.  Albumen  (white  of  egg),  of  which,  however,  not  too  much  should 
be  given  at  one  time,  lest  the  precipitate  formed  by  the  mercuric  salt  and 
albumin  be  redissolved.  The  antidote  should  be  followed  by  an  emetic  to 
remove  the  albuminous  mercury  compound. 


QUESTIONS. — 281.  How  is  silver  obtained  from  the  native  ores,  and  how  may 
it  be  prepared  from  silver  coin  ?  282.  State  of  silver  nitrate :  its  composition, 
mode  of  preparation,  properties,  and  names  by  which  it  is  known.  283.  Give 
analytical  reactions  for  silver.  284.  How  is  mercury  found  in  nature ;  how  is 
it  obtained  from  the  native  ore ;  what  are  its  physical  and  chemical  properties  ? 
285.  Mention  the  three  oxides  of  mercury ;  how  are  they  made,  what  is  their 
composition,  what  is  their  color  and  solubility?  286.  State  of  the  two  chlorides 
of  mercury :  their  names,  composition,  mode  of  preparation,  solubility,  color, 
and  other  properties.  287.  Mention  the  same  of  the  two  iodides,  as  above,  for 
the  chlorides.  288.  State  the  difference  between  mercuric  sulphate,  basic  mer- 
curic sulphate,  and  mercurous  sulphate.  289.  What  is  formed  when  ammonium 
hydroxide,  calcium  hydroxide,  potassium  or  sodium  hydroxide  is  added  to  either 
mercurous  or  mercuric  chloride  ?  290.  Give  tests  answering  for  any  mercury 
compound,  and  tests  by  which  mercuric  compounds  may  be  distinguished  from 
mercurous  compounds. 


204 


METALS  AND  THEIR  COMBINATIONS. 


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AESENIC.  205 

30.   ARSENIC. 

As  =*=  74  9. 

General  remarks  regarding-  the  metals  of  the  arsenic  group. 
The  metals  belonging  to  either  of  the  five  groups  considered  hereto- 
fore, show  much  resemblance  to  each  other  in  their  chemical  prop- 
erties, and  consequently  in  their  combinations.  This  is  much  less 
the  case  among  the  six  metals  (As,  Sb,  Sn,  Au,  Pt,  Mo)  which  are 
classed  together  in  this  group.  In  fact,  the  only  resemblance  which 
unites  these  metals  is  the  insolubility  of  their  sulphides  in  dilute 
acids  and  the  solubility  of  these  sulphides  in  ammonium  sulphide 
(or  alkali  hydroxides),  with  which  they  form  soluble  double  com- 
pounds ;  the  oxides  have  also  a  tendency  to  form  acids.  In  all  other 
respects  no  general  resemblance  exists  between  these  metals.  Arsenic 
and  antimony  have  many  properties  in  common,  and  resemble  in 
many  respects  the  non-metallic  elements  phosphorus  and  nitrogen,  as 
may  be  shown  by  a  comparison  of  their  hydrides,  oxides,  acids,  and 
chlorides. 


NH3  NA  NA  NCI,. 

PH3  PA  P2Qs  H3P04  PC13. 

AsH3  AsA  AsA  H3AsO4  AsCl3. 

SbH3  SbA  SbA  SbCl3. 


Arsenic.  Found  in  nature  sometimes  in  the  native  state,  but 
generally  as  sulphide  or  arsenide.  One  of  the  most  common  arsenic 
ores  is  the  arsenio-sulphide  of  iron,  or  mispielcel,  FeSAs.  Realgar  is 
the  native  red  sulphide,  As2S2,  and  orpiment  or  auripigment,  the  native 
yellow  sulphide,  As2S3.  Arsenides  of  cobalt,  nickel,  and  other  metals 
are  not  infrequently  met  with  in  nature.  Certain  mineral  waters 
contain  traces  of  arsenic  compounds. 

Arsenic  may  be  obtained  easily  by  heating  arsenous  oxide  with 
charcoal,  or  by  allowing  vapors  of  arsenous  oxide  to  pass  over  char- 
coal heated  to  redness  : 

As2O3  -f  3C  =  SCO  -f  2As. 

In  both  cases  the  arsenic,  when  liberated  by  the  reducing  action  of 
the  charcoal,  exists  in  the  form  of  vapor,  which  condenses  in  the 
cooler  part  of  the  apparatus  as  a  steel-gray  metallic  mass,  which 
when  exposed  to  the  amospheric  air,  loses  the  metallic  lustre  in  conse- 
quence of  the  formation  of  a  film  of  oxide. 

When  pure,  arsenic  is  odorless  and  tasteless  ;  it  is  very  brittle,  and 
volatilizes  unchanged  and  without  melting  when  heated  to  180°  C. 


206  METALS  AND  THEIR  COMBINATIONS. 

(356°  F.),  without  access  of  air.  Heated  in  air,  it  burns  with  a 
bluish-white  light,  forming  arsenous  oxide.  Although  insoluble  in 
water,  yet  water  digested  with  arsenic  soon  contains  some  arsenous 
acid  in  solution,  the  oxide  of  arsenic  being  formed  by  oxidation  of 
the  metal  by  the  oxygen  absorbed  in  the  water. 

Arsenic  is  used  in  the  metallic  state  as  fly-poison,  and  in  some 
alloys,  chiefly  in  shot,  an  alloy  of  lead  and  arsenic. 

The  molecule  of  arsenic  contains  four  atoms,  and  not  two,  like 
most  elements.  It  is  trivalent  in  some  compounds,  quinquivalent  in 
others. 

Arsenous  oxide,  Acidum  arsenosum,  As2O3  =  197.8  (Arsenious 
oxide,  White  arsenic,  Arsenic  trioxide,  Arsenous  anhydride,  improperly 
Arsenous  acid).  This  compound  is  frequently  obtained  as  a  by- 
product in  metallurgical  operations  during  the  manufacture  of  metals 
from  ores  containing  arsenic.  Such  ores  are  roasted  (heated  in  a 
current  of  air),  when  arsenic  is  converted  into  arsenous  oxide,  which, 
at  that  temperature,  is  volatilized  and  afterward  condensed  in 
chambers  or  long  flues. 

Arsenous  oxide  is  a  heavy,  white  solid,  occurring  either  as  an 
opaque,  slightly  crystalline  powder,  or  in  transparent  or  semi-trans- 
parent masses  which  frequently  show  a  stratified  appearance; 
recently  sublimed  arsenous  oxide  exists  as  the  amorphous  semi- 
transparent  glassy  mass  known  as  vitreous  arsenous  oxide,  which 
gradually  becomes  opaque  and  ultimately  resembles  porcelain.  This 
change  is  due  to  a  rearrangement  of  the  molecules  into  crystals  which 
can  be  seen  under  the  microscope. 

The  two  modifications  of  arsenous  oxide  differ  in  their  solubility 
in  water,  the  amorphous  or  glassy  variety  dissolving  more  freely  than 
the  crystallized.  One  part  of  arsenous  oxide  dissolves  in  from  30  to 
80  parts  of  cold  and  in  15  parts  of  boiling  water,  the  solution  having 
at  first  a  faint  acrid  and  metallic,  and  afterward  a  sweetish  taste. 
This  solution  contains  the  arsenous  oxide  not  as  such,  but  as  arsenous 
acid,  H3AsO3,  which  compound,  however,  cannot  be  obtained  in  an 
isolated  condition,  but  is  known  in  solution  only  : 

As2O3  +  3H2O  =  2H3AsO3. 

A  second  arsenous  acid,  termed  met-arsenous  acid  or  meta-arsenous 

acid,  HAsO2,  is  known  in  some  salts,  as,  for  instance,  in  sodium  met- 

arsenite,  NaAsO2,  which   salt   may   be  obtained   by  the  action  of 

arsenous  oxide  on  the  carbonate,  bicarbonate,  or  hydroxide  of  sodium  : 

As2O3  +  2NaOH  =  2NaAsO2  +  H2O. 


ARSENIC.  207 

When  heated  to  about  218°  C.  (424°  F.)  arsenous  oxide  is  volatil- 
ized without  melting ;  the  vapors,  when  condensed,  form  small, 
shining,  eight-sided  crystals  ;  when  heated  on  charcoal,  it  is  deoxi- 
dized, giving  off,  at  the  same  time,  an  odor  resembling  that  of  garlic. 

Arsenous  oxide  is  frequently  used  in  the  arts  and  for  manufacturing 
purposes,  as,  for  instance,  in  the  manufacture  of  green  colors,  of 
opaque  white  glass,  in  calico-printing,  as  a  powerful  antiseptic  for 
the  preservation  of  organic  objects  of  natural  history,  and,  finally,  as 
the  substance  from  which  all  arsenic  compounds  are  obtained. 

The  official  solution  of  arsenous  acid,  Liquor  acidi  arsenosi,  is  a  1 
per  cent,  solution  of  arsenous  oxide  in  water  to  which  5  per  cent,  of 
diluted  hydrochloric  acid  has  been  added. 

The  official  solution  of  arsenite  of  potassium,  Liquor  potassii  arse- 
nitis,  or  Fowler's  solution,  is  made  by  dissolving  1  part  of  arsenous 
oxide  and  2  parts  of  potassium  bicarbonate  in  94  parts  of  water  and 
adding  3  parts  of  compound  tincture  of  lavender ;  the  solution  con- 
tains the  arsenic  as  potassium  met-arsenite. 

Arsenic  oxide,  As2O5  (Arsenic  pentoxide,  Anhydrous  arsenic  acid). 
When  arsenous  oxide  is  heated  Avith  nitric  acid,  it  becomes  oxidized 
and  is  converted  into  arsenic  acid,  H3AsO4,  from  which  the  water 
may  be  expelled  by  further  heating,  when  arsenic  oxide  is  left : 
2H3AsO4  =  As2O5  -f  3H2O. 

Arsenic  oxide  is  a  heavy,  white,  solid  substance  which,  in  contact 
with  water,  is  converted  into  arsenic  acid.  This  acid  resembles  phos- 
phoric acid  not  only  in  composition,  but  also  in  forming  metarsenic 
and  pyroarsenic  acid  under  the  same  conditions  under  which  the  cor- 
responding phosphoric  acids  are  formed.  The  salts  of  arsenic  acid, 
the  arsenates,  also  resemble  in  their  constitution  the  corresponding 
phosphates. 

Arsenic  oxide  and  arsenic  acid  are  used  largely  as  oxidizing  agents 
in  the  manufacture  of  aniline  colors. 

Disodium  hydrogen  arsenate,  Sodii  arsenas,  Na2HAsO4.7H2O 
=  311.9  (Sodium  arsenate).  This  salt  is  made  by  fusing  arsenous 
oxide  with  carbonate  and  nitrate  of  sodium. 

As203  +  2NaN03  +  Na2CO3  =  Na4As2O7  +  N2O3  +  CO2. 

Sodium  pyroarsenate  is  formed,  nitrogen  trioxide  and  carbon 
dioxide  escaping.  By  dissolving  in  water  and  crystallizing,  the 
official  salt  is  obtained  in  colorless,  transparent  crystals  : 

15H20  =  2(Na2HAsO4.7H2O). 


208  METALS  AND  THEIR  COMBINATIONS. 

Liquor  sodii  arsenatis  is  a  1  per  cent,  solution  of  sodium  arsenate 
in  water. 

Hydrogen  arsenide,  AsH3  (Arsine,  Arsenetted  or  arseniuretted 
hydrogen).  This  compound  is  formed  always  when  either  arsenous 
or  arsenic  oxides  or  acids,  or  any  of  their  salts,  are  brought  in  con- 
tact with  nascent  hydrogen,  for  instance,  with  zinc  and  diluted 
sulphuric  acid,  which  evolve  hydrogen  : 

As203  -f  12H  =  2AsH3  -f  3H2O. 
As205  +  16H  =  2AsII3  +  5H2O. 
AsCl3  +  6H  =  AsH3  +  3HC1. 

Hydrogen  arsenide  is  a  colorless,  highly  poisonous  gas,  having  a 
strong  garlic  odor.  Ignited,  it  burns  with  a  bluish  flame,  giving  off 
white  clouds  of  arsenous  oxide  : 

2AsH3  +  6O  =  As2O3  +  3H2O. 

When  a  cold  plate  (porcelain  answers  best)  is  held  in  the  flame  of 
arsenetted  hydrogen,  a  dark  deposit  of  metallic  arsenic  (arsenic  spots) 
is  produced  upon  the  plate  (in  a  similar  manner  as  a  deposit  of 
carbon  is  produced  by  a  common  luminous  flame).  The  formation  of 
this  metallic  deposit  may  be  explained  by  the  fact  that  the  heat  of  the 
flame  decomposes  the  gas,  and  that,  furthermore,  of  the  two  liberated 
elements,  arsenic  and  hydrogen,  the  latter  has  the  greater  affinity  for 
oxygen.  In  the  centre  of  the  flame,  to  which  but  a  limited  amount 
of  oxygen  penetrates,  the  latter  is  taken  up  by  the  hydrogen,  arsenic 
being  present  in  the  metallic  state  until  it  burns  in  the  outer  cone  of 
the  flame.  It  is  this  liberated  arsenic  which  is  deposited  upon  a  cold 
substance  held  in  the  flame. 

Arsenetted  hydrogen,  when  heated  to  redness,  is  decomposed  into 
its  elements  ;  by  passing  the  gas  through  a  glass  tube  heated  to  red- 
ness, the  liberated  arsenic  is  deposited  in  the  cooler  part  of  the  tube, 
forming  a  bright  metallic  ring. 

Sulphides  of  arsenic.  Two  sulphides  of  arsenic  are  known  and 
iiave  been  mentioned  above  as  the  native  disulphide  or  realgar,  As2S2, 
and  the  trisulphide  or  orpiment,  As2S3.  Disulphide  of  arsenic  is  an 
orange-red,  fusible,  and  volatile  substance,  used  as  a  pigment ;  it 
may  be  made  by  fusing  together  the  elements  in  the  proper  propor- 
tions. Trisulphide  is  a  golden-yellow,  fusible,  and  volatile  substance, 
which  also  may  be  obtained  by  fusing  the  elements,  or  by  precipitating 
an  arsenic  solution  by  hydrogen  sulphide  (Plate  V.,  1).  Both  sul- 
phides of  arsenic  are  sulpho-acids,  uniting  with  other  metallic  sul- 


ARSENIC.  209 

pbides  to  form  sulpho-salts,  as,  for  instance,  K2S.As2S3,  or  (NH4)2S. 
As2S3.  These  compounds  are  known  as  sulph-arsenides. 

Arsenous  iodide,  Arseni  iodidum,  AsI3  =  454.5  (Iodide  of 
arsenic),  may  be  obtained  by  direct  combination  of  the  elements,  and 
forms  orange-red  crystalline  masses,  soluble  in  water  and  alcohol,  but 
decomposed  by  boiling  with  either  of  these  liquids.  It  is  used  in  the 
official  preparation,  Solution  of  arsenic  and  mercuric  iodide,  Donovan's 
solution,  which  is  made  by  dissolving  one  part  each  of  arsenous  iodide 
and  mercuric  iodide  in  98  parts  of  water. 

Analytical  reactions. 
(Use  arsenous  oxide,  As.2O3,  and  sodium  arsenate,  NajHAsO^  respectively.) 

1.  Add  hydrogen  sulphide  to  an  aqueous  solution  of  arsenous  oxide : 
a  yellow  coloration  but  no  precipitate  is  formed  until  some  hydro- 
chloric acid  is  added,  when  yellow  arsenic  trisulphide,  As2S3  (Plate 
V.,  1)  is  precipitated  : 

As2O3  +  3H2S  =  3H2O  +  As2S3; 
or 

2H3AsO3  -f  3H2S  =  6H2O  +  As2S3. 

When  hydrogen  sulphide  is  added  to  a  cold  solution  of  arsenic 
oxide  or  of  an  arsenate,  acidified  with  hydrochloric  acid,  a  yellow 
mixture  of  arsenic  trisulphide,  As2S3,  and  sulphur  is  slowly  pre- 
cipitated : 

2H3As04  +  5H2S  =  8H20  +  As2S3  +  2S. 

When  the  same  substances  act  upon  one  another  in  hot  solution,  and 
when  also  an  excess  of  hydrogen  sulphide  (preferably  a  current  of  the 
gas)  is  used,  yellow  arsenic  pentasulphide  is  precipitated  : 

As2O5  +  5H2S  =  5H2O  +  As2S5 ; 
or 

2H3AsO4  +  5H2S  =  8H2O  +  As2S5. 

2.  Add  ammonium  sulphide  or  any  alkali  hydroxide  to  the  yellow 
precipitate  of  arsenous  or  arsenic  sulphide  :  the  precipitates  are  readily 
dissolved,  but  may  be  reprecipitated  by  neutralizing  with  an  acid. 

3.  Ammonio-nitrate  of  silver  (silver  nitrate  to  which  enough  of 
water  of  ammonia  has  been  added  to  redissolve  the  precipitate  at  first 
formed)  produces  in  neutral  solutions  of  arsenous  acid  a  yellow  precipi- 
tate of  silver  arsenite,  Ag3AsO3  (Plate  V.,  3) ;  in  arsenic  acid  solu- 
tions a  reddish-brown  precipitate  of  silver  arsenate,  Ag3AsO4  (Plate 
V.,  4).     The  two  precipitates  are  soluble  in  both  alkalies  and  acids. 

14 


210  METALS  AND  THEIR  COMBINATIONS. 

Silver  arsenite  dissolved  in  water  of  ammonia  and  boiled  forms  silver 
arsenate  and  metallic  silver. 

4.  Ammonio-sulphate  of  copper  (made   similarly   to    ammonio- 
nitrate  of  silver  from  cupric  sulphate)  added  to  neutral   arsenous 
solutions  produces  a  green  precipitate  of  cupric  arsenite  (CuHAsO3) 
known  as  Scheele's  green  (Plate  V.,  2).     (Arsenite  of  copper  mixed 
with  cupric   acetate  is  known  as   Schweinfurth  green).     The    same 
reagent  produces  in  neutral  solutions  of  an  arsenate  a  similar  green 
precipitate  of  cupric  arsenate,  CuHAsO4.     Cupric  arsenite   boiled 
with  potassium  hydroxide  forms  potassium  arsenate  and  red  cuprous 
oxide. 

Instead  of  using  for  the  above  tests  the  ammonio  salts,  silver 
nitrate  or  cupric  sulphate  may  be  added  to  the  acid  (or  neutral)  solu- 
tion of  arsenic,  then  adding  water  of  ammonia  carefully  in  small 
quantities  until  a  neutral  reaction  has  been  obtained,  when  the  pre- 
cipitate is  formed. 

5.  Soluble  arsenates  give  white  precipitates  with  soluble  salts  of 
barium,  calcium,  magnesium,  zinc,  and  some  other  metals;  soluble 
arsenites  do  not.     Arsenates  give,  on  heating  with  ammonium  molyb- 
date,  a  yellow  precipitate  of  ammonium  arseno-molybdate,  (NH4)3 
AsO4.10MoO3. 

6.  Heat  any  dry  arsenic  compound,  after  being  mixed  with  some 
charcoal  and  dry  potassium  carbonate  in  a  very  narrow  test-tube  (or, 

FIG.  13. 


better,  in  a  drawn-out  glass  tube  having  a  small  bulb  on  the  end) : 
the  arsenic  compound  is  decomposed  and  the  metallic  arsenic  deposited 
as  a  metallic  ring  in  the  upper  part  of  the  contraction.  (Fig.  13.) 


V. 


ARSENIC.      ANTIMONY.      TIN. 


Arsenoiis  sulphide,  precipitated 
from  arsenous  solutions  by  hydrogen 
sulphide. 


Cupric  arsei»ite,precipitated  from 
arsenous  solutions  by  cupric-ammo- 
nium  sulphate. 


Silver  arsenite,  precipitated  from 
arsenous  solutions  by  silver  nitrate. 


Silver  arseiiate,  precipitated  from 
arsenic  solutions  by  silver  nitrate. 


Aiitiinonoua  sulphide,  precipi- 
tated from  solutions  of  antimony  by 
hydrogen  sulphide. 


Native  or  crystallized  aiitimo- 
iions  sulphide. 


Staiinous  sulphide,  precipitated 
from  stannous  solutions  by  hydrogen 
sulphide. 


Stannic  sulphide,  precipitated 
from  stannic  solutions  by  hydrogen 
sulphide. 


ARSENIC. 


211 


FIG.  14. 


7.  Heat  arsenous  or  arsenic  oxide  upon  a  piece  of  charcoal  by 
means  of  a  blowpipe ;  a  characteristic  odor  of  garlic  is  perceptible. 

8.  Reinsch's  test.     A  thin  piece  of  copper,  having  a  bright  metallic 
surface,  placed  in  a  slightly  acidified  solution  of  arsenic  becomes,  upon 
heating  the  solution,  coated  with  a  dark  steel-gray  deposit  of  arsenic, 
which  can  be  vaporized  by  application  of  heat. 

9.  Bettendorff's  test.     Add  to  any  arsenic  compound,  dissolved  in 
concentrated  hydrochloric  acid,  an  equal  volume  of  freshly  prepared 
solution  of  stannous  chloride  in  hydrochloric  acid,  add  a  small  piece 
of  tin-foil,  and  apply  heat :  a  brown  color  or  precipitate  is  formed, 
due  to  the  separation  of  arsenic. 

10.  Gutzeit's  test.     Place  a  small  piece  (about  1  gramme)  of  pure 
zinc  in  a  test-tube,  add  about  5  c.c.  of  dilute  (5  per  cent.)  sulphuric 
acid  and  a  few  drops  of  any  arsenic  solution,  which  should  not  be 
alkaline.     Fasten  over  the  mouth  of  the  test  tube  a  cap  made  of  three 
thicknesses  of  pure  filter  paper,  and  moisten  the  upper 

paper  with  a  drop  of  a  saturated  solution  of  silver 
nitrate  in  water,  acidulated  with  about  1  per  cent,  of 
nitric  acid.  (Fig.  14.)  Place  the  tube  in  a  box  so  as 
to  exclude  all  light,  and  examine  the  paper  cap  after 
awhile.  Upon  it  will  appear  a  bright  yellow  stain, 
rapidly  if  the  quantity  of  arsenic  be  considerable,  slowly 
if  it  be  small.  Upon  moistening  the  yellow  stain  with 
water  the  color  changes  to  brown  or  black.  The  action 
of  hydrogen  arsenide  upon  silver  nitrate  in  the  absence 
of  water  takes  place  with  the  formation  of  a  yellow 
compound,  thus : 

AsH3  +  6AgN03  =  3HN03  +  Ag3As.(AgNO3)3. 

In  the  presence  of  water  metallic  silver  is  separated, 
showing  a  black  or  brown  color : 

AsH3  +  6AgNO3  "+  6H2O  =  6HNO3  +  H3AsO3  +  6Ag. 

Compounds  of  antimony  treated  in  the  above  manner 
produce  a  dark  spot  upon  the  paper,  but  cause  no  pre- 
vious yellow  color. 

11.  Fleitmann^s  test.     This  is  similar  to  the  previous 

test,  the  chief  difference  being  that  hydrogen  is  evolved  in  alkaline 
solution,  which  has  the  advantage  that  the  presence  of  antimony  does 
not  interfere,  because  this  metal  does  not  form  antimonetted  hydrogen 
in  alkaline  solutions. 

Place  about  1  gramme  of  pure  zinc  in  a  test-tube,  add  about  5  c.c. 


212  MEIALS  AND  THEIR  COMBINATIONS. 

of  potassium  hydroxide  solution  and  a  few  drops  of  the  arsenic  solu- 
tion, which  should  not  be  acid.  Provide  paper  cap  as  described  in 
previous  test,  and  set  the  test-tube  in  a  box  containing  sand  heated 
to  about  90°  C.  (194°  F.).  A  brown  or  black  stain  of  metallic 
silver  will  appear  upon  the  paper. 

12.  Marsh's  test.  While  this  test  is  not  used  now  for  qualitative 
determinations  as  much  as  formerly,  it  is  of  great  value  because  it 
may  serve  for  collecting  the  total  amount  of  arsenic  present  in  a 
specimen,  thus  permitting  quantitative  estimation.  The  apparatus 
(Fig.  15)  used  for  performing  this  test  consists  of  a  glass  vessel  (flask 
or  Woulf's  bottle)  provided  with  a  funnel-tube  and  delivery-tube 
(bent  at  right  angles),  which  is  connected  with  a  wider  tube,  filled 
with  pieces  of  calcium  chloride  or  plugs  of  asbestos ;  this  drying-tube 
is  again  connected  with  a  piece  of  hard  glass  tube,  about  one  foot 
long,  having  a  diameter  of  J  inch,  drawn  out  at  intervals  of  about 
3  inches,  so  as  to  reduce  its  diameter  to  J-  inch.  Hydrogen  is  gener- 
ated in  the  flask  by  the  action  of  sulphuric  acid  on  zinc,  and  ex- 
amined for  its  purity  by  heating  the  glass  tube  to  redness  at  one  of 

FIG.  15. 


Marsh's  apparatus  for  detection  of  arsenic. 

its  wide  parts  for  at  least  30  minutes;  if  no  trace  of  a  metallic  mirror 
is  formed  at  the  constriction  beyond  the  heated  point,  the  gas  and  the 
substances  used  for  its  generation  may  be  pronounced  free  from 
arsenic.  (Both  zinc  and  sulphuric  acid  often  contain  arsenic.) 

After  having  thus  demonstrated  the  purity  of  the  hydrogen,  the 
suspected  liquid,  which  must  contain  the  arsenic  either  as  oxide  or 


ARSENIC. 


213 


FIG.  16. 


chloride  (not  as  sulphide),  is  poured  into  the  flask  through  the  funnel- 
tube.  If  arsenic  is  present  in  not  too  small  quantities,  the  gas  ignited 
at  the  end  of  the  glass  tube  shows  a  flame  decidedly  different  from 
that  of  burning  hydrogen.  The  flame  becomes  larger,  assumes  a 
bluish  tint,  and  emits  an  odor  of  garlic,  while  above  it  a  white  cloud 
appears  which  is  more  or  less  dense ;  a  cold  test-tube  held  inverted 
over  the  flame  will  be  covered  upon  its  walls  with  a  white  deposit  of 
minute  octahedral  crystals  of  arse  nous  oxide;  a  piece  of  cold  porce- 
lain held  in  the  flame  becomes  coated  with  a  brown  stain  (arsenic 
spot)  of  metallic  arsenic.  (See  explanation  above  in  connection  with 
arsenetted  hydrogen.) 

The  glass  tube  heated,  as  above  mentioned,  at  one  of  its  wide  parts, 
will  show  a  bluish-black  metallic  mirror  at  the  constriction  beyond. 

If  quantitative  determination  is  desired,  the  glass  tube  is  heated  in 
two  places  so  as  to  cause  all  hydrogen  arsenide  to  be  decomposed.  To 
collect,  however,  the  arsenic  from  any  gas  that  might  escape,  the  end 
of  the  tube  is  inverted  and  placed  into  solution  of  nitrate  of  silver, 
which  is  decomposed  by  the  hydrogen  arsenide,  silver  and  arsenous 
acid  being  formed.  The  arsenic  solution  should  be 
introduced  into  the  hydrogen  generator  in  small  por- 
tions, so  as  to  produce  not  more  hydrogen  arsenide 
at  a  time  than  can  be  decomposed  by  the  method 
given. 

The  only  element  which,  tinder  the  same  condi- 
tions, forms  spots  and  mirrors  similar  to  arsenic,  is 
antimony;  there  are,  however,  sufficiently  reliable 
tests  to  distinguish  arsenic  spots  from  those  of  anti- 
mony. 

Arsenic  spots  treated  with  solution  of  hypochlorites 
(solution  of  bleaching-powder)  dissolve  readily ;  anti- 
mony spots  are  not  affected.  When  nitric  acid  is 
added  to  an  arsenic  spot,  evaporated  to  dryness  and 
moistened  with  a  drop  of  silver  nitrate,  it  turns 
brick-red;  antimony  spots  treated  in  like  manner 
remain  white.  Arsenic  spots  dissolved  in  ammonium 
sulphide  and  evaporated  to  dryness  show  a  bright  yellow,  antimony 
spots  an  orange-red  residue. 

Fig  16  represents  a  simpler  form  of  Marsh's   apparatus,  which 
generally  will  answer  for  students'  tests. 

Preparatory   treatment   of  organic   matter   for   arsenic   analysis.     If 
organic  matter  is  to  be  examined  for  arsenic  (or  for  any  other  metallic  poison) 


Student's  appa- 
ratus for  making 
arsenic  spots. 


214  METALS  AND  THEIR  COMBINATIONS. 

it  ought  to  be  treated  as  follows :  The  substance,  if  not  liquid,  is  cut  into  pieces, 
well  mashed  and  mixed  with  water ;  the  liquid  or  semi-liquid  substance  is 
heated  in  a  porcelain  dish  over  a  steam  bath  with  hydrochloric  acid  and  potas- 
sium chlorate  until  the  mass  has  a  uniform  light  yellow  color  and  has  no  longer 
an  odor  of  chlorine.  By  this  operation  all  poisonous  metals  (lead  and  silver 
excepted,  because  insoluble  silver  chloride  and  possibly  insoluble  lead  sulphate 
are  formed)  are  rendered  soluble  even  when  present  as  sulphides,  and  may 
now  be  separated  by  nitration  from  some  remaining  solid  matter.  The  clear 
solution  is  heated  and  treated  with  hydrosulphuric  acid  gas  for  several  hours, 
when  arsenic  and  all  metals  of  the  arsenic  and  lead  groups  are  precipitated  as 
sulphides,  a  little  organic  matter  also  being  precipitated  generally. 

The  precipitate  is  collected  upon  a  small  filter  and  treated  with  warm  ammo- 
nium sulphide,  which  dissolves  the  sulphides  of  arsenic  and  antimony,  leaving 
behind  the  sulphides  of  the  lead  group,  which  may  be  dissolved  in  nitric,  or,  if 
mercury  be  present,  in  nitro-hydrochloric  acid,  and  the  solution  tested  by  the 
methods  mentioned  for  the  respective  metals.  The  ammonium  sulphide  solu- 
tion is  evaporated  to  dryness,  this  residue  mixed  with  nitrate  and  carbonate  of 
sodium,  and  the  mixture  fused  in  a  small  porcelain  crucible.  By  the  oxidizing 
action  of  the  nitrate,  both  sulphides  are  converted  into  the  higher  oxides, 
arsenic  forming  sodium  arsenate,  antimony  forming  antimonic  oxide.  By 
treating  the  mass  with  warm  water,  sodium  arsenate  is  dissolved  and  may  be 
filtered  off,  while  antimonic  oxide  remains  undissolved,  and  may  be  dissolved  in 
hydrochloric  acid.  Both  solutions  may  now  be  used  for  making  the  respective 
tests  for  arsenic  or  antimony. 

Antidotes.  Moist,  recently  prepared  ferric  hydroxide  or  dialyzed  iron  are 
the  best  antidotes,  insoluble  ferric  arsenite  or  arsenate  being  formed.  Vomit- 
ing should  be  induced  by  tickling  the  fauces  or  by  administering  zinc  sulphate, 
but  not  tartar  emetic. 


QUESTIONS. — 291.  Which  metals  belong  to  the  arsenic  group?  what  are  their 
characteristics?  292.  Which  non-metallic  elements  does  arsenic  resemble? 
Mention  some  of  the  compounds  showing  this  analogy.  293.  How  is  arsenic 
obtained  in  the  metallic  state ;  what  are  its  physical  and  chemical  properties ; 
how  does  heat  act  upon  it?  294.  What  is  white  arsenic?  State  its  compo- 
sition, mode  of  manufacture,  appearance,  solubility,  and  other  properties. 
295.  Which  three  solutions,  containing  arsenic,  are  official,  and  what  is  their 
composition?  296.  How  is  arsenic  acid  obtained  from  arsenous  oxide,  and 
which  arsenate  is  official?  297.  State  composition  and  properties  of  arse- 
netted  hydrogen,  and  explain  its  formation.  What  use  is  made  of  it  in  testing 
for  arsenic?  298.  State  the  composition  of  realgar,  orpiment,  Scheele's  green, 
and  Schweinfurth  green.  299.  Give  a  detailed  description  of  the  process  by 
which  arsenic  can  be  detected  in  organic  matter.  300.  Describe  in  detail  the 
principal  tests  for  arsenic. 


ANTIMONY.  215 


31.  ANTIMONY— TIN-GOLD-PLATINUM— MOLYBDENUM. 

Antimony,  Sb  :  =  119.6  (Stibium).  This  metal  is  found  in  nature 
chiefly  as  the  trisulphide,  Sb2S3,  an  ore  which  is  known  as  black  anti- 
mony j  crude  antimony,  or  stibnite. 

The  metal  is  obtained  from  the  sulphide  by  roasting,  when  it  is 
converted  into  oxide,  which  is  reduced  by  charcoal.  Antimony  is  a 
brittle,  bluish-white  metal,  having  a  crystalline  structure ;  it  fuses  at 
450°  C.  (842°  F.),  and  may  at  a  higher  temperature  be  distilled  with- 
out change,  provided  air  is  excluded  ;  heated  in  air  it  burns  bril- 
liantly. 

Antimony  is  used  in  a  number  of  important  alloys,  for  instance, 
in  type-metal,  an  alloy  of  lead,  tin,  and  antimony. 

Antimony  trisulphide,  Antimonii  sulphidum,  Sb2S3  =  335.2 
(Antimonous  sulphide,  Antimony  sulphide).  The  above-mentioned 
native  sulphide,  the  black  antimony,  is  found  generally  associated 
with  other  ores  or  minerals,  from  which  it  is  freed  by  heating  the 
masses,  when  the  antimony  sulphide  fuses  and  is  made  to  run  oif  into 
suitable  vessels  for  cooling.  Thus  obtained  it  forms  steel-gray  masses 
of  a  metallic  lustre,  and  a  striated,  crystalline  fracture,  forming  a 
grayish-black,  lustreless  powder,  which  is  insoluble  in  water,  but 
soluble  in  hydrochloric  acid  with  liberation  of  hydrogen  sulphide. 

When  finely  powdered  antimonous  sulphide  is  treated  with  water  of  ammonia 
to  remove  any  traces  of  arsenic  (which  is  frequently  found  in  this  ore)  and  the 
washed  sulphide  dried,  the  purified  antimony  sulphide  of  the  U.  S.  P.  is  obtained. 

Antimonous  sulphide  found  in  nature  is  crystallized  and  steel-gray 
(Plate  V.,  6),  but  it  may  be  obtained  also  in  an  amorphous  condition 
as  an  orange-red  (Plate  V.,  5)  powder  by  passing  hydrogen  sulphide 
through  an  antimouous  solution.  By  heating  the  orange-red  sul- 
phide, it  is  converted  into  the  black  variety. 

Sulphurated  antimony,  Antimonium  sulphuratum  ( Oxysulphide 
of  antimony,  Kermes  mineral),  chiefly  antimony  trisulphide  with  some 
antimony  oxide.  This  preparation  is  made  by  boiling  purified  anti- 
monous sulphide  with  solution  of  sodium  hydroxide,  and  adding  to 
the  hot  solution  sulphuric  acid  as  long  as  a  precipitate  is  formed, 
which  is  collected  and  dried. 

It  is  a  reddish-brown  amorphous  powder,  insoluble  in  water, 
soluble  in  hydrochloric  acid  or  sodium  hydroxide. 


216  METALS  AND  THEIR  COMBINATIONS. 

The  sulphides  and  oxides  of  antimony,  like  those  of  arsenic,  combine  with 
many  metallic  sulphides  or  oxides  to  form  sulpho-salts  or  oxy-salts.  Thus  the 
sodium  sulph-antimonite,  Na3SbS3,  and  the  sodium  antimonite,  NaSb02,  are 
formed  when  antimonous  sulphide  is  boiled  with  sodium  hydroxide. 

Sb2S3  +  4NaOH  =  Na3SbS3  -f  NaSbO2  -f  2H2O. 

By  the  addition  of  sulphuric  acid,  both  salts  are  decomposed,  sodium  sulphate 
is  formed,  and  antimonous  sulphide  is  precipitated  : 

Na3SbS3  +  NaSbO2  +  2H2SO4  =±  Sb2S3  +  2Na2SO4  +  2H2O. 

While  the  above  is  the  principal  reaction,  there  is  formed  also  some  anti- 
mony oxide. 

Experiment  37.  Boil  about  2  grammes  of  finely  powdered  black  antimony 
with  a  solution  of  2  grammes  of  sodium  hydroxide  in  80  c.c.  of  water  for  about 
one  hour,  stirring  frequently  and  occasionally  adding  water  to  preserve  the 
same  volume.  Filter  the  warm  liquid  through  paper  or  muslin  and  add  dilute 
sulphuric  acid  so  long  as  it  produces  a  precipitate.  Collect,  wash,  and  dry  the 
precipitated  red  powder,  which  is  chiefly  amorphous  antimonous  sulphide  with 
oxide. 

Antimony  pentasulphide,  Sb2S5  (Golden  sulphuret  of  antimony). 
A  red  powder,  which,  like  antimonous  sulphide,  forms  sulpho-salts. 
It  may  be  obtained  by  precipitation  of  acid  solutions  of  antimonic 
acid  by  hydrosulphuric  acid. 

Antimonous  chloride,  SbCl3  (Antimony  terchloride,  Suiter  of  anti- 
mony). Obtained  by  boiling  the  native  sulphide  with  hydrochloric 

acid: 

Sb2S3  +  6HC1  =  3H2S  +  2SbCl3. 

The  clear  solution  is  evaporated  and  the  remaining  chloride  dis- 
tilled, when  it  is  obtained  as  a  white,  crystalline,  semi-transparent 
mass. 

By  passing  chlorine  over  antimonous  chloride  it  is  converted  into 
antimonic  chloride,  SbCl5,  which  is  a  fuming  liquid. 

Experiment  38.  Boil  about  2  grammes  of  black  antimony  with  10  c.c.  of 
hydrochloric  acid  until  most  of  the  sulphide  is  dissolved.  Set  aside  for  sub- 
sidence, pour  off  the  clear  solution  of  antimonous  chloride,  evaporate  to  about 
half  its  volume  and  use  solution  for  next  experiment. 

Antimonous  oxide,  Antimonii  oxidum,  Sb2O3  =  287.2  (Anti- 
mony trioxide).  When  antimonous  chloride  is  added  to  water,  decom- 
position takes  place,  and  an  oxychloride  of  antimony,  2SbCl35Sb2O3, 
is  precipitated : 

12SbCl3  +  15H2O  =  2SbCl3.5Sb203  4-  30HC1. 

This  white  precipitate  was  formerly  known  as  powder  of  Algaroth. 


ANTIMONY.  217 

It  is  completely  converted  into  oxide  by  treating  it  with  sodium  car- 
bonate : 

2SbCl3  5Sb203  +  3Na2CO3  ==  6Sb2O3  +  6NaCl  +  3CO2. 

The  precipitate  when  washed  and  dried  is  a  heavy,  grayish-white, 
tasteless  powder,  insoluble  in  water,  soluble  in  hydrochloric  acid,  and 
also  in  a  warm  solution  of  tartaric  acid.  Antimonous  oxide,  while 
yet  moist,  dissolves  readily  in  potassium  acid  tartrate,  forming  the 
double  tartrate  of  potassium  and  antimony,  or  tartar  emetic,  which  salt 
will  be  more  fully  considered  hereafter. 

Experiment  39.  Pour  the  antimonous  chloride  solution  (obtained  by  Ex- 
periment 38),  which  should  have  been  boiled  sufficiently  to  expel  all  hydrogen 
sulphide,  into  100  c.c.  of  water,  wash  by  decantation  the  white  precipitate  of 
oxychloride  thus  obtained,  and  add  to  it  an  aqueous  solution  of  about  1  gramme 
of  sodium  carbonate.  After  effervescence  ceases,  collect  the  precipitate  on  a 
filter,  wash  well  and  treat  some  of  the  precipitate,  while  yet  moist,  with  a  solu- 
tion of  potassium  acid  tartrate,  which  dissolves  it  readily,  forming  tartar  emetic. 
(For  the  latter  compound  see  index.) 

Antidotes.  Poisonous  doses  of  any  preparation  of  antimony  are  generally 
quickly  followed  by  vomiting  :  if  this,  however,  have  not  occurred,  the  stomach- 
pump  must  be  applied.  Tannic  acid  in  any  form,  or  recently  precipitated  ferric 
hydroxide,  should  be  administered. 

Analytical  reactions. 
(A  solution  of  antimonous  chloride,  SbCl3,  may  be  used.) 

1.  Add  hydrogen  sulphide  to  an  acidified  solution  of  antimony: 
an  orange-red  precipitate  of  antimonous  or  autimonic  sulphide  (Sb2S3 
or  Sb2S5)  is  produced  (Plate  V.,  5). 

2.  Add  ammonium  sulphide  to  the  precipitated  sulphide  of  anti- 
mony :  this  is  dissolved  and  may  be  re-precipitated  by  neutralizing 
with  an  acid. 

3.  Produce  a  concentrated  solution  of  antimonous   chloride    by 
evaporation  or  by  dissolving  the  sulphide  in  hydrochloric  acid,  and 
pour  it  into  water:  a  white  precipitate  of  oxychloride  is  formed.  (See 
explanation  above.) 

4.  Add  sodium  hydroxide,  ammonium  hydroxide,  or  sodium  car- 
bonate :  in  either  case  white  antimonous  hydroxide  Sb(OH3)  is  pro- 
duced, which  is  soluble  in  sodium  hydroxide. 

5.  Boil  a  piece  of  metallic  copper  in  the  solution  of  antimonous 
chloride :  a  black  deposit  of  antimony  is  formed  upon  the  copper. 
By  heating  the  latter  in  a  narrow  test-tube,  the  antimony  is  volatil- 
ized and  deposited  as  a  white  incrustation  of  antimonous  oxide  upon 
the  glass. 


218  METALS  AND  THEIR  COMBINATIONS. 

6.  Use  Gutzeit's  or  Marsh's  test  as  described  under  analytical  re- 
actions for  arsenic. 

Tin,  Sn  =  118.8  (Stannum).  This  metal  is  found  in  nature  chiefly 
as  stannic  oxide  or  tin-stone,  SnO2,  from  which  the  metal  is  easily 
obtained  by  heating  with  coal : 

Sn02  +  2C  =  Sn  +  2CO. 

Tin  is  an  almost  silver-white,  very  malleable  metal,  fusing  at  the 
comparatively  low  temperature  of  228°  C.  (440°  F.).  It  is  used  in 
many  alloys,  in  the  silvering  of  looking-glasses  by  tin-amalgam,  and 
chiefly  in  the  manufacture  of  tin-plate,  which  is  sheet-iron  covered 
with  a  thin  layer  of  tin. 

Tin  is  bivalent  in  some  compounds,  quadrivalent  in  others.  These 
combinations  are  distinguished  as  stannous  and  stannic  compounds. 

Stannoas  chloride,   SnCl2  (Protochloride  of  tin).     Obtained  by 
dissolving  tin  in  hydrochloric  acid  by  the  aid  of  heat : 
Sn  +  2HC1  =  SnCl2  +  2H. 

Sufficiently  evaporated,  the  solution  yields  crystals  of  the  composi- 
tion SnCl2.2H2O.  Stannous  chloride  is  a  strong  deoxidizing  agent, 
frequently  used  as  a  reagent  for  arsenic,  mercury,  and  gold,  which 
metals  are  precipitated  from  their  solutions  in  the  metallic  state.  It 
is  used  also  in  calico  printing. 

Stannic  chloride,  SnCl4  (Perchloride  of  tin).  Stannous  chloride 
may  be  converted  into  stannic  chloride  either  by  passing  chlorine 
through  its  solution  or  by  heating  with  hydrochloric  and  nitric  acids. 

Analytical  reactions. 
(Stannous  chloride,  SnCl,2,  and  stannic  chloride,  SnCl4,  may  be  used.) 

1.  Add  hydrogen  sulphide  to  solution  of  a  stannous  salt:  brown 
stannous  sulphide  is  precipitated  (Plate  V.,  7) : 

SnCl2  +  H2S  =  2HC1  f  SnS. 

The  precipitate  is  soluble  in  ammonium  sulphide. 

2.  Add  hydrosulphuric  acid  to  a  solution  of  a  stannic  salt :  yellow 
stannic  sulphide  is  precipitated  (Plate  Y.,  8) : 

SnCl2  +  2H2S  =  4HC1  -f  SnS2. 

The  precipitate  is  soluble  in  ammonium  sulphide. 

3.  Sodium  or  potassium  hydroxide  added  to  a  stannous  salt,  pro- 
duces a  white  precipitate  of  stannous  hydroxide,  Sn(OH)2.     The  same 


GOLD.  219 

reagents  added  to  a  stannic  salt  produce  white  stannic  acid,  H2SnO3. 
Both  precipitates  are  soluble  in  excess  of  the  alkali. 

Gold,  Au  =  196.7  (Aurum).  Gold  occurs  in  nature  chiefly  in  the 
free  state,  often  associated  with  silver,  copper,  and  possibly  with  other 
metals.  This  impure  gold  is  separated  from  most  of  the  adhering 
sand  and  rock  by  a  mechanical  process  of  washing,  in  which  advan- 
tage is  taken  of  the  high  specific  gravity  of  the  metallic  masses.  The 
remaining  mixture  of  heavy  material  is  treated  with  mercury,  which 
dissolves  gold  and  silver,  leaving  behind  most  other  impurities.  The 
gold  amalgam  is  placed  in  a  retort  and  heated,  when  the  mercury 
distils  over,  while  the  gold  is  left  behind.  If  this  should  contain 
silver,  the  metals  may  be  separated  by  treating  the  alloy  with  hot 
sulphuric  acid,  which  dissolves  silver,  leaving  gold  behind. 

Pure  gold  is  too  soft  for  general  use,  and  therefore  is  alloyed  with 
various  proportions  of  silver  and  copper.  American  coin  is  an  alloy 
of  90  parts  of  gold  and  10  parts  of  copper;  jeweller's  gold  contains 
generally  75  per  cent.  (18  carat)  of  gold,  the  other  25  per  cent,  being 
copper  and  silver ;  the  varying  proportions  are  well  indicated  by  the 
color. 

Gold  is  not  affected  by  either  hydrochloric,  nitric,  or  sulphuric 
acid,  but  is  dissolved  by  nitro-hydrochloric  acid,  by  free  chlorine  or 
bromine,  and  by  mercury,  with  which  it  forms  an  amalgam. 

Gold  is  trivalent  generally,  as  in  auric  chloride,  AuCl3,  but  most 
likely  also  univalent  in  some  compounds,  as  in  aurous  chloride,  AuCl. 

Auric  chloride,  AuCl3  (Gold  chloride).  Obtained  by  dissolving 
pure  gold  in  nitro-hydrochloric  acid  and  evaporating  the  solution  to 
dryness.  A  mixture  of  equal  parts  of  auric  chloride  and  sodium 
chloride  is  official  under  the  name  of  gold  and  sodium  chloride.  It  is 
an  orange-yellow,  very  soluble  powder. 

Analytical  reactions. 
(Auric  chloride,  AuCl3,  may  be  used.) 

1.  Add  hydrogen  sulphide  to  solution  of  gold  :  brown  auric  sul- 
phide, Au2S3,  is  precipitated,  which  is  soluble  in  yellow  ammonium 
sulphide. 

2.  Add  ferrous  sulphate  to  solution  of  gold  and  set  aside  for  a  few 
hours :    metallic  gold  is  precipitated  as  a  dark  powder,  which  by 
fusion  is  converted  into  a  metallic  mass. 


220  METALS  AND  THEIR  COMBINATIONS. 

3.  Many  other  reagents  cause  the  separation  of  metallic  gold  from 
its  solution,  as,  for  instance,  oxalic  acid,  sulphurous  and  arsenous 
acids,  potassium  nitrite,  etc. 

Platinum,  Pt  =  194.3.  Platinum,  like  gold,  is  found  in  nature  in 
the  free  state,  the  chief  supply  being  derived  from  the  Ural  moun- 
tains, where  it  is  found  associated  with  a  number  of  metals  (iridium, 
ruthenium,  osmium,  palladium,  rhodium)  resembling  platinum  in 
their  properties. 

Platinum  is  of  great  importance  and  value  on  account  of  its  high 
fusing-point  and  its  resistance  to  the  action  of  most  chemical  agents, 
for  which  reason  it  is  used  in  the  manufacture  of  vessels  serving  in 
chemical  operations. 

Platinum,  when  dissolved  in  nitro-hydrochloric  acid,  forms  platinic 
chloride,  PtCl4,  a  salt  frequently  used  as  a  reagent  for  potassium  or 
ammonium  salts,  with  which  it  forms  insoluble  double  chlorides  of 
the  composition  PtCl4.(KCl)2  and  PtCl4.(NH4Cl)2.  By  heating  the 
latter  salt  sufficiently  it  is  decomposed  and  metallic  platinum  is  left 
as  a  gray  spongy  mass. 

Molybdenum,  Mo  =  95.9.  This  metal  is  found  in  nature  chiefly 
as  sulphide,  MoS2,  from  which,  by  roasting,  molybdic  oxide,  MoO3, 
is  obtained.  The  oxide,  when  dissolved  in  water,  forms  an  acid 
which  combines  with  metals,  forming  a  series  of  salts  termed 
molybdates.  Of  interest  is  ammonium  molybdate,  a  solution  of  which 
in  nitric  acid  is  an  excellent  reagent  for  phosphoric  acid,  with  which 
it  forms  a  yellow  precipitate,  insoluble  in  acids,  soluble  in  ammonium 
hydroxide. 

QUESTIONS. — 301.  How  is  antimony  found  in  nature,  and  what  are  the  prop- 
erties of  this  metal  ?  302.  State  the  composition  of  antimonous  sulphide,  and 
its  color  when  crystallized  and  amorphous.  303.  How  do  hydrochloric  acid 
and  alkali  hydroxides  act  upon  antimonous  sulphide  ?  304.  What  is  the  sul- 
phurated antimony  of  the  U.  S.  P.  ?  305.  Mention  the  two  chlorides  of  anti- 
mony and  state  their  properties.  306.  How  is  antimonous  oxide  made,  and 
what  is  it  used  for?  307.  Give  tests  for  antimony.  308.  State  the  use  made 
of  tin  in  the  metallic  state ;  mention  the  two  chlorides  of  tin,  and  what  stannous 
chloride  is  used  for.  309.  How  are  gold  and  platinum  found  in  nature ;  by 
what  acid  may  they  be  dissolved,  and  what  is  the  composition  of  the  com- 
pounds formed  ?  310.  Which  is  the  most  important  compound  of  molybdenum, 
and  what  is  it  used  for  ? 


THE  ARSENIC  GROUP. 


221 


Summary  of  analytical  characters  of  metals  of  the  arsenic 

group. 


Arsenic. 

Antimony. 

Tin. 

Gold. 

Platinum. 

Hydrogen  sulphide    . 

Yellow  pre- 
cipitate. 

Orange 
precipitate 

Yellow 
or  brown 

Black 
precipitate 

Dark- 
brown 

precipitate. 

precipitate. 

Precipitate  heated  \ 
in  strong  hydro-  [• 

Insoluble. 

Soluble. 

Soluble. 

Insoluble. 

Insoluble. 

chloric  acid  .     .  J 

Potassium  hvdroxide 

White 

White 

Brownish 

With  ex- 

precipitate 

precipitate. 

precipitate, 

cess  of 

soluble 

hydro- 

in excess. 

chloric 

acid  a 

.Ammonia  water 

White 

White 

Brownish 

VfkllfYW 

precipitate. 

precipitate. 

yellow 

j  tJllUVV 

precipi- 

precipitate. 

tate. 

Outzeit's  test     .    .    . 

Yellow  stain 

Dark  stain. 

turning  dark 

with  water. 

Fleitmann's  test 

Dark  stain. 

Y. 

ANALYTICAL  CHEMISTRY. 


32.    INTRODUCTORY  REMARKS  AND  PRELIMINARY 
EXAMINATION. 

General  remarks.  Analytical  chemistry  is  that  part  of  chemistry 
which  treats  of  the  different  analytical  methods  by  which  substances 
are  recognized  and  their  chemical  composition  determined.  This 
determination  may  be  either  qualitative  or  quantitative,  and,  accord- 
ingly, a  distinction  is  made  between  a  qualitative  analysis,  by  which 
simply  the  nature  of  the  elements  (or  groups  of  elements)  present  in 
the  substance  under  examination  is  determined,  and  a  quantitative 
analysis,  by  which  also  the  exact  amount  of  these  elements  is  ascer- 
tained. 

In  this  book  qualitative  analysis  will  be  considered  chiefly,  as  the 
methods  for  quantitative  determinations  of  the  different  elements  are 
so  numerous  and  so  varied  that  a  detailed  description  of  them  would 
occupy  more  space  than  can  be  devoted  to  analytical  chemistry  in  this 
work.  Some  brief  directions  concerning  quantitative  determinations, 
especially  by  volumetric  methods,  are  given  in  Chapter  36.  Every- 
one studying  analytical  chemistry  should  do  it  practically,  that  is, 
should  perform  for  himself  in  a  laboratory  all  those  reactions  which 
have  been  mentioned  heretofore  as  characteristic  of  the  different  ele- 
ments and  their  compounds,  and,  furthermore,  should  make  himself 
acquainted  with  the  methods  by  which  substances  are  recognized 
when  mixed  with  others,  by  analyzing  various  complex  substances. 

Such  a  course  of  practical  work  in  a  suitable  laboratory  is  of  the 
greatest  advantage  to  all  studying  chemistry,  and  students  cannot  be 
too  strongly  advised  to  avail  themselves  of  any  facilities  offered  in 
performing  chemical  experiments,  analytically  or  otherwise. 

Apparatus  needed  for  qualitative  analysis. 

1.  Iron  stand.     (Fig.  17.) 

2.  Bunsen  lamp  with  flexible  tube  (Fig.  17),  or  (where  without  gas-supply) 

spirit-lamp  and  alcohol. 
(222) 


INTRODUCTORY  REMARKS. 


223 


3.  Test-tube  stand  and  one  dozen  assorted  test-tubes.    (Fig.  18.) 

4.  Three  small  beakers  from  100  to  150  c.c.  capacity.     (Fig.  19,  A.) 

5.  Two  flasks  of  100  to  150  c.c.  capacity.    (Fig.  19,  B.) 

FIG.  17. 


FIG.  18. 


FIG.  19. 


6.  Wash-bottle  of  about  400  c.c.  capacity.     (Fig.  20,  A. ) 

7.  Three  small  glass  funnels,  about  one  and  a  half  to  two  inches  in  diameter. 

(Fig.  20,  B.) 


224 


ANALYTICAL  CHEMISTRY. 


8.  A  few  pieces  of  glass  tubing  about  ten  inches  long,  and  some  India-rubber 

tubing  to  fit  the  glass  tubing. 

9.  Three  glass  rods. 

FIG.  20. 


10.  Three  small  porcelain  evaporating  dishes,  about  two  inches  in  diameter 

(Fig.  21,  A.) 

11.  Blowpipe.    (Fig.  21,  B.) 

12.  Crucible  tongs.     (Fig.  21,  C.) 


FIG.  21. 


13.  Round  and  triangular  file 

14.  Wire  gauze,  about  six  inches  square,  or  sand  tray. 

15.  One  square  inch  of  platinum  foil  (not  too  light),  and  six  inches  of 

platinum  wire. 

16.  Filter-paper. 

17.  Pair  of  scissors. 

18.  One  or  two  dozen  assorted  corks. 

19.  Sponge  and  towel. 

20.  Two  watch-glasses. 

21.  Small  pestle  and  mortar.     (Fig.  21,  D.) 

22.  Small  porcelain  crucible. 

23.  Small  platinum  crucible.     (Fig.  21,  E.) 

24.  Wire  triangle  to  support  the  crucible.     (Fig.  21,  F.) 


INTRODUCTORY  REMARKS.  225 

Reagents  needed  in  qualitative  analysis. 

a.  Liquids. 

1.  Sulphuric  acid,  sp.  gr.  1.84,  H2SO4. 

2.  Sulphuric  acid  diluted,  sp.  gr   1.068  (1  part  sulphuric  acid,  9  parts  water). 

3.  Hydrochloric  acid,  sp  gr.  1.16,  HC1. 

4.  Hydrochloric  acid  diluted,  sp.  gr.  1.049   (6  parts  hydrochloric  acid,  13  parts 

water). 

5.  Nitric  acid,  sp.  gr.  1.42,  HNOS. 

6.  Acetic  acid,  sp.  gr  1  048,  C2H4O2. 

7.  Hydrogen  sulphide,  either  the  gas  or  its  solution  in  water,  H2S. 

8.  Ammonium  sulphide,  (NH4)2S. 

9.  Ammonium  hydroxide  (water  of  ammonia),  NH4OH. 

10.  Ammonium  carbonate,  (NH4)2CO3      A  solution  of  one  part  of  the  commercial 

salt  in  a  mixture  of  four  parts  of  water  and  one  part  of  water  of  ammonia. 

11.  Ammonium  chloride,  NH4C1;  ten  per  cent  solution. 

12    Ammonium  oxalate,  (NH4)2C2O4;  five  per  cent,  solution. 

13.  Ammonium  molybdate,  (NH4)2MoO4.     A  five  per  cent  solution  of  the  salt  in  a 

mixture  of  equal  parts  of  water  and  nitric  acid. 

14.  Sodium  hydroxide,  NaOH. 

15.  Sodium  carbonate,  Na2CO3 


16.  Sodium  phosphate,  Na2HPO4. 

17.  Sodium  acetate,  NaC2H3O2. 

18.  Potassium  chromate,  K2CrO4. 

19.  Potassium  dichromate,  K2Cr2O7. 

20.  Potassium  iodide,  KL 

21    Potassium  ferrocyanide,  K4Fe(CN)6. 


Ten  per  cent,  solutionst 


Five  per  cent,  solutions. 


22.  Potassium  ferricyanide,  K6Fe2(CN)12. 
23    Potassium  sulphocyanate,  KCNS. 

24.  Magnesium  sulphate,  MgSO4. 

25.  Barium  chloride,  BaCl2.  [•    Ten  per  cent,  solutions. 

26.  Calcium  chloride,  CaCl2. 

27.  Calcium  hydroxide,  Ca( OH)2  (lime-water).         |    Saturated  solutions. 

28.  Calcium  sulphate,  CaSO4. 

29.  Ferric  chloride,  Fe2Cl6.  "1 

30.  Lead -acetate,  Pb.(C2H3O2)2. 

31.  Silver  nitrate,  AgNO3.  Five  per  cent,  solutions. 

32.  Mercuric  chloride,  HgCl2- 

33.  Platinic  chloride,  PtCl4.  J 

34.  Stannous  chloride,  SnCl2.2H2O;  ten  per  cent,  solution. 

35.  Solution  of  indigo 

36.  Alcohol,  C2H5OH 

37.  Sodium  cobaltic  nitrite  solution,  Co2(NO2)6.6NaNO2  -|-  H2O.     Four  grammes  of 

cobaltous  nitrate,  Co(NO3)2  6H2O,  and  10  grammes  of  sodium  nitrite,  NaNO2, 
are  dissolved  in  about  50  c.c.  of  water,  2  c.c  of  acetic  acid  are  added,  and  then 
water  to  make  100  c  c. 

38.  Alkaline  mercuric-potassium  iodide  solution  (Nessler's  solution).     Five  grammes 

of  potassium  iodide  are  dissolved  in  hot  water,  and  to  this  is  added  a  hot 
solution,  made  by  dissolving  25  grammes  of  mercuric  chloride  in  10  c.c.  of 
water.  To  the  turbid  red  mixture  is  added  a  solution  made  by  dissolving  16 

15 


226  ANALYTICAL  CHEMISTRY. 

grammes  of  potassium  hydroxide  in  40  cc  of  water,  and  the  whole  diluted  to 
100  c  c  Some  mercuric  iodide  deposits  on  cooling,  and  may  be  left  in  the 
bottle,  the  clear  solution  being  decanted  as  needed. 

b.  Solids. 

1.  Litmus  or  blue  and  red  litmus  paper. 
2    Turmeric  paper. 

3.  Sodium  carbonate,  dried,  Na2CO3. 

4.  Sodium  biborate,  borax,  Na2Bo4O7  10H2O. 

5.  Sodium-ammonium-hydrogen  phosphate  (microcosmic  salt), 

Na(NH4)HPO4.4H2O. 

6.  Potassium  carbonate,  K2CO3. 

7.  Potassium  nitrate,  KNO3. 

8.  Potassium  chlorate,  KC1O3. 

9.  Potassium  permanganate,  KMnO4. 
10-  Potassium  cyanide,  KCN. 

11.  Calcium  hydroxide,  Ca(OH)2. 

12.  Ferrous  sulphide,  FeS. 

13.  Ferrous  sulphate,  FeSO4.7H2O. 

14.  Manganese  dioxide,  MnO2. 

15.  Zinc,  granulated,  Zn. 

16.  Copper,  Cu 

17.  Cupric  oxide,  CuO 

18.  Cupric  sulphate,  CuSO4  5H2O. 
19    Tartaric  acid,  H2C4H4O6. 

20.  Tannic  acid,  H.CUH9O9 

21.  Pyrogallic  acid,  C6H3(OH)3. 

22.  Diphenylamine,  (C6H5)2NH. 

23.  Starch,  C6H10O5 

While  the  apparatus  and  reagents  here  enumerated  are  the  more 
important  ones,  the  analyst  will  occasionally  require  others  not  men- 
tioned in  the  above  list. 

General  mode  of  proceeding- in  qualitative  analysis.  Every 
step  taken  in  analysis  should  be-  properly  written  down  in  a  note- 
book, and  these  remarks  should  be  made  directly  after  a  reaction  has 
been  performed,  and  not  after  the  nature  of  the  substance  has  been 
revealed  by  perhaps  numerous  reactions. 

Not  only  the  reactions  by  which  positive  results  have  been  obtained 
should  be  noted,  but  also  those  tests  and  reagents  mentioned  which 
have  been  applied  with  negative  results — that  is,  which  have  been 
applied  without  revealing  the  presence  of  any  substance,  or  any  group 
of  substances.  Such  negative  results  are,  however,  positive  in  so  far 
as  they  prove  the  absence  of  a  certain  substance,  or  certain  substances, 
for  which  reason  they  are  of  direct  value,  and  should  be  noted. 

In  comparing,  finally,  the  result  obtained  by  the  analysis  with  the 


INTROD  UCTOE  Y  REMARKS.  22? 

notes  taken  during  the  examination,  none  of  them  should  be  contra- 
dictory to  the  conclusions  drawn.  If,  for  instance,  the  preliminary 
examination  showed  the  substance  to  have  been  volatilized  by  heating 
upon  platinum  foil  with  the  exception  of  a  very  slight  residue,  and  if, 
afterward,  other  tests  show  the  presence  of  ammonia  and  hydro- 
chloric acid  and  the  absence  of  everything  else,  and  if,  then,  the  con- 
clusion be  drawn  that  the  substance  is  pure  ammonium  chloride,  this 
conclusion  must  be  incorrect,  because  pure  ammonium  chloride  is 
wholly  volatile,  and  does  not  leave  a  residue.  It  will  then  be  the  task 
of  the  operator  to  find  where  the  mistake  occurred,  and  to  correct  it. 

Use  of  reagents.  A  mistake  made  by  most  beginners  in  analyz- 
ing is  the  use  of  too  large  quantities  both  of  the  substance  applied 
for  testing  and  of  the  reagents  added.  This  excessive  use  of  material 
is  not  only  a  waste  of  money,  but,  what  is  of  greater  importance,  a 
waste  of  time.  Some  experience  in  analyzing  will  soon  convince  the 
student  of  the  truth  contained  in  this  remark,  and  will  also  enable 
him  to  select  the  correct  quantities  of  materials  to  be  used,  which 
rarely  exceed  0.2-1.0  gramme.  A  smaller  amount  frequently  may 
answer,  and  a  much  larger  quantity  may  occasionally  be  needed,  as, 
for  instance,  in  cases  where  highly  diluted  reagents,  such  as  calcium 
sulphate  solution,  lime-water,  hydrogen  sulphide  water,  etc.,  are 
applied. 

Preliminary  examination.  This  examination  includes  the  fol- 
lowing points : 

1.  Physical  properties.     Solid  or  liquid;  crystallized  or  amor- 
phous; color,  odor,  hardness,  gravity,  etc.     (On  account  of  possible 
poisonous  properties,  the  greatest  care  should  be  exercised  in  tasting 
a  substance.) 

2.  Action  on  litmus.     Examined  by  holding  litmus-paper  in  the 
liquid,  or  by  placing  the  powdered  solid  upon  red  and  blue  litmus- 
paper,  moistened  with  water.     (It  should  be  remembered  that  many 
normal  salts,  as,  for  instance,  aluminum  sulphate,  ferrous  sulphate, 
etc.,  have  an  acid  reaction  to  litmus-paper,  and  that  such  a  reaction 
consequently  is  not  conclusive  of  the  presence  of  a  free  acid,  nor  even 
of  an  acid  salt.) 

3.  Heating-  on  platinum  foil  or  in  a  dry  glass  tube,  open  at 
both  ends.     (If  the  substance  to  be  examined  be  a  liquid,  it  should 


228  ANALYTICAL  CHEMISTRY. 

be  evaporated  in  a  small  porcelain  dish  to  see  whether  a  solid  residue 
be  left  or  not.  If  a  residue  be  left,  it  should  be  treated  like  a  solid.) 
The  heating  of  a  small  quantity  of  a  solid  substance  upon  platinum 
foil  held  over  the  flame  of  a  Bunsen  burner  or  of  an  alcohol  lamp,  is 
a  test  which  should  never  be  omitted,  as  it  discloses  in  most  cases  the 
fact  whether  the  substance  is  of  an  organic  or  inorganic  nature.  Most 
organic  (non- volatile)  substances,  when  thus  heated,  will  burn  with 
a  luminous  flame,  leaving  in  many  cases  a  black  residue  of  carbon, 
which,  upon  further  heating,  disappears.  In  cases  where  the  organic 
nature  of  a  compound  is  not  clearly  demonstrated  by  heating  on  plati- 
num foil,  the  substance  is  heated  with  an  excess  of  cupric  oxide  in  a 
test-tube  or  other  glass  tube,  provided  with  a  delivery -tube,  which 
passes  into  lime-water.  Upon  heating  the  mixture,  the  carbon  of  the 
organic  matter  is  converted  into  carbon  dioxide,  which  renders  lime- 
water  turbid. 

The  analytical  processes  by  which  the  nature  of  an  organic  sub- 
stance is  determined,  are  not  considered  in  this  part  of  the  book,  but 
will  be  mentioned  when  considering  the  carbon  compounds. 

An  inorganic  substance,  heated  on  platinum  foil,  may  either  be 
volatilized,  fused,  change  color,  become  oxidized,  suifer  decomposition, 
or  remain  unchanged.  (See  Table  I.,  page  232.) 

PIG.  22.  FIG.  23. 


Heating  of  solids  in  bent  glass  tube.  Heating  on  charcoal  by  means  of  blowpipe. 

Some  substances,  containing  small  quantities  of  water  enclosed 
between  the  crystals  (common  salt,  for  instance),  decrepitate  when 
heated,  the  small  fragments  being  thrown  from  the  foil;  such  sub- 


INTRODUCTORY  REMARKS.  229 

stances  should  be  heated  in  a  dry  test-tube  to  expel  the  water  and 
then  be  examined  on  platinum  foil. 

In  many  cases  it  is  preferable  to  heat  the  substance  in  a  bent  glass 
tube,  as  shown  in  Fig.  22,  instead  of  on  platinum  foil,  because  vola- 
tile products  evolved  during  the  process  of  heating  may  become  re- 
condensed  in  the  cooler  part  of  the  tube,  and  thus  saved  for  further 
examination. 

The  presence  of  water,  sulphur,  mercury,  arsenic,  etc.,  may  often 
be  readily  demonstrated  by  this  mode  of  operating. 

4.  Heating-  on  charcoal  by  means  of  the  blowpipe.     This  test 
reveals  the  presence  of  chlorates  and  nitrates  by  the  vivid  combus- 
tion of  the  charcoal  (known  as  deflagration),  which  takes  place  in 
consequence  of  the  oxidizing  action  of  these  substances. 

Arsenic  is  indicated  by  a  characteristic  odor  of  garlic. 

5.  Heating-  on  charcoal  with  sodium  carbonate  and  potas- 
sium cyanide.     A  small  quantity  of  the  finely  powdered  substance 
is  mixed  with  twice  its  weight  of  potassium  cyanide  and  dry  sodium 
carbonate.     This  mixture  is  placed  in  a  small  hole  made  in  a  piece 
of  charcoal,  and  heat  applied  by  means  of  the  blowpipe  (see  Fig.  23). 
Many  metallic  compounds  may  be  recognized  by  this  test,  the  metals 
being  liberated  and  found  as  metallic  globules  or  shining  particles  in 
the  fused  mass  after  this  has  been  removed  from  the  charcoal  and 
washed  with  water  in  a  small  mortar.     (See  Fig.  24.) 

FIG.  24. 


A  characteristic  incrustation  is  formed  by  some  metals,  due  to  the 
precipitation  of  a  metallic  oxide  around  the  heated  spot  on  the  char- 
coal. 

If  sulphur  as  such,  or  in  any  form  of  combination,  be  present  in 
the  substance  examined  by  this  test,  the  fused  mass  contains  a  sulphide 
of  the  alkali  (hepar),  which  may  be  recognized  by  placing  it  on  a 
piece  of  bright  silver  (coin)  moistened  with  a  drop  of  water,  when  the 


230  ANALYTICAL  CHEMISTRY. 

silver  will  be  stained  black  in  consequence  of  the  formation  of  silver 
sulphide.  The  presence  of  the  alkali  sulphide  may  also  be  demon- 
strated by  the  addition  of  a  few  drops  of  hydrochloric  acid  to  the 
fused  mass,  when  hydrogen  sulphide  is  evolved  and  may  be  recog- 
nized by  its  odor. 

6.  Flame  tests.  Many  substances  impart  a  characteristic  color 
to  a  non-luminous  flame.  The  best  mode  of  performing  this  test  is 
as  follows :  A  platinum  wire  is  cleaned  by  washing  in  hydrochloric 
acid  and  water,  and  heating  it  in  the  flame  until  the  latter  is  no 
longer  colored.  One  end  of  the  wire  is  fused  in  a  short  piece  of 
glass  tubing  (see  Fig.  25),  the  other  end  is  bent  so  as  to  form  a  small 

FIG.  25. 


loop,  which  is  heated,  dipped  into  the  substance  to  be  examined,  and 
again  held  in  the  lower  part  of  the  flame,  which  then  becomes  colored. 

Some  substances  show  the  color-test  after  being  moistened  with 
hydrochloric  or  sulphuric  acid. 

A  second  method  of  showing  flame  reactions  is  to  mix  the  substance 
with  alcohol  in  a  small  dish ;  the  alcohol,  upon  being  ignited,  shows 
a  colored  flame,  especially  in  the  dark. 

7.  Colored  borax  beads.  The  compounds  of  some  metals  when 
fused  with  glass,  impart  to  it  characteristic  colors.  For  analytical 
purposes  not  the  silica-glass,  but  borax-glass  is  generally  used.  This 
latter  is  made  by  dipping  the  loop  of  a  platinum  wire  in  powdered 
borax  and  heating  it  in  the  flame  (directly,  or  by  means  of  the  blow- 
pipe) until  all  water  has  been  expelled  and  a  colorless,  transparent 
bead  has  been  formed.  To  this  colorless  bead  a  little  of  the  finely 
powdered  substance  is  added  and  the  bead  strongly  heated.  The 
metallic  compound  is  chemically  acted  upon  by  the  boric  acid,  aborate 
being  formed  which  colors  the  bead  more  or  less  intensely,  according 
to  the  quantity  of  the  metallic  compound  used. 

Some  metals  (copper,  for  instance)  forming  two  series  of  compounds, 
give  different  colors  to  the  bead  when  present  in  either  the  higher  or 
lower  state  of  oxidation. 

By  modifying  the  blowpipe  flame  so  as  either  to  oxidize  (by 
supplying  an  excess  of  atmospheric  oxygen)  or  deoxidize  (by  allowing 
some  unburnt  carbon  to  remain  in  the  flame),  the  metallic  compound 


INTRODUCTORY  REMARKS.  231 

in  the  bead  may  be  made  to  assume  the  higher  or  lower  state  of 
oxidation.  A  copper  bead  may  thus  be  changed  from  blue  to  red  or 
red  to  blue,  the  blue  bead  containing  the  copper  in  the  cupric,  the 
red  bead  in  the  cuprous  form.  In  some  cases  microcosmic  salt, 
NaNH4HPO4,  is  used  for  making  the  bead. 

8.  Liquefaction  of  solid  substances.  Most  solid  substances 
have  to  be  dissolved  for  analysis.  The  solution  obtained  may  be 
either  a  simple  or  chemical  solution.  In  a  simple  solution  the  dis- 
solved body  retains  all  of  its  original  properties,  with  the  exception 
of  its  shape,  and  may  be  re-obtained  by  evaporation.  Sodium 
chloride  and  sugar  dissolved  in  water  form  simple  solutions.  A 
chemical  solution  is  one  in  which  the  chemical  composition  of  the  sub- 
stance has  been  changed  during  the  process  of  dissolving,  as,  for 
instance  when  calcium  carbonate  is  dissolved  in  hydrochloric  acid; 
this  ,  solution  now  contains  and  leaves  on  evaporation  calcium 
chloride.  The  solvents  used  are  water,  or  the  mineral  acids  for 
substances  insoluble  in  water,  especially  dilute,  or,  if  necessary,  strong 
hydrochloric  acid.  The  dissolving  action  of  the  acid  should  be  facil- 
itated by  the  aid  of  heat.  Nitric  or  even  nitro-hydrochloric  acid 
may  have  to  be  used  in  some  cases. 

Three  mistakes  are  frequently  made  by  beginners  in  dissolving 
substances  in  acids,  viz. :  The  substance  is  not  powdered  as  finely  as 
it  should  be  ;  sufficient  time  is  not  given  for  the  acid  to  act ;  too 
large  an  excess  of  the  acid  is  used. 

If  a  substance  is  partly  dissolved  by  water  and  partly  by  one  or 
more  other  solvents,  it  may  be  well  to  examine  the  different  solutions 
separately. 

Substances  insoluble  in  water  and  in  acids  have  to  be  rendered 
soluble  by  fusion  with  a  mixture  of  potassium  and  sodium  carbonate, 
or  with  potassium  acid  sulphate,  or  by  the  action  of  hydrofluoric  acid. 

The  insoluble  sulphates  of  the  alkaline  earths,  when  fused  with  the 
alkaline  carbonates,  are  con  verted  into  carbonates,  while  the  sulphates 
of  the  alkalies  are  formed.  The  latter  compounds  may  be  eliminated 
by  washing  the  fused  mass  with  water  and  filtering :  the  solid  residue 
upon  the  filter  contains  the  carbonates  of  the  alkaline  earths,  which 
may  be  dissolved  in  hydrochloric  acid. 

Insoluble  silicates  may  be  decomposed  by  the  methods  mentioned 
on  page  98. 

QUESTIONS.— 311.  What  is  analytical  chemistry,  and  what  is  the  object  of 
qualitative  and  of  quantitative  analysis?  212.  What  properties  of  a  substance 


232 


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SEPARATION  OF  METALS  INTO  DIFFERENT  GROUPS.       233 


33.   SEPARATION  OF  METALS  INTO  DIFFERENT  GROUPS. 

General  remarks.  The  preliminary  examination  will,  in  most 
cases,  decide  whether  or  not  a  metal  or  metals  are  present  in  the  sub- 
stance to  be  examined.  If  there  be  metals,  the  solution  should  be 
treated  according  to  Table  II.,  page  236,  in  order  to  find  the  group 
or  groups  to  which  these  metals  belong,  and  also  to  separate  them 
into  these  groups,  the  individual  nature  of  the  metals  themselves 
being  afterward  demonstrated  by  special  methods. 

The  simplest  method  of  separating  from  each  other  the  55  metals 
known,  if  all  were  in  one  solution,  would  be  to  add  successively  55 
different  reagents,  each  of  which  should  form  an  insoluble  compound 
with  but  one  of  the  metals.  By  separating  this  insoluble  compound 
from  the  metals  remaining  in  solution  (by  filtration),  and  by  thus  pre- 
cipitating one  metal  after  the  other,  they  all  could  be  easily  separated. 
We  have,  however,  no  such  55  reagents,  and  are,  consequently,  com- 
pelled to  precipitate  a  number  of  metals  together,  and  the  reagents 
used  for  this  purpose  are  known  as  group-reagents. 

They  are : 

1.  Hydrogen  sulphide,  added  to  the  solution  previously  acidified  by 
hydrochloric  acid.     Precipitated  are  :  the  metals  of  the  arsenic  and 
lead  groups  as  sulphides. 

2.  Ammonium  sulphide,  added  after  supersaturating  with  ammonium 
hydroxide.     Precipitated  are :  the  metals  of  the  iron  group  and  of 
the  earths  as  sulphides  or  hydroxides. 

3.  Ammonium  carbonate.      Precipitated  are :    the  metals  of    the 
alkaline  earths  as  carbonates. 

4.  In  solution  are  left :  the  metals  of  the  alkalies  and  magnesium. 
The  order  in  which   these  group-reagents  are  added  cannot  be 

should  be  noticed  first  in  making  a  qualitative  analysis  ?  313.  By  what  tests 
may  organic  compounds  be  distinguished  from  inorganic  compounds  ?  314. 
Explain  the  terms  decrepitation  and  deflagration.  315.  Mention  some  sub- 
stances which  are  completely  volatilized  by  heat,  some  which  are  fusible,  and 
some  which  are  not  changed  by  heating  them.  316.  What  is  meant  by  "  hepar/' 
and  which  element  is  indicated  by  the  formation  of  hepar  ?  317.  Mention  some 
metals  which  may  be  liberated  from  their  compounds  by  heating  on  charcoal 
with  potassium  cyanide  and  carbonate.  318.  Which  metallic  compounds  and 
which  acids  are  capable  of  coloring  a  non-luminous  flame  ?  Name  the  colors 
imparted.  319.  State  the  metals  which  impart  characteristic  colors  to  a  borax 
bead.  320.  Which  solvents  are  used  for  liquefying  solids,  and  what  precau- 
tions should  be  observed  in  this  operation  ? 


234  ANALYTICAL  CHEMISTRY. 

reversed  or  changed,  because  ammonium  sulphide  added  first  would 
precipitate  not  only  the  metals  of  the  iron  group  and  the  earths,  but 
also  the  metals  of  the  lead  group ;  ammonium  carbonate  would  pre- 
cipitate also  most  of  the  heavy  metals. 

For  the  same  reasons,  in  separating  metals  of  the  different  groups,  the  group- 
reagents  must  be  added  in  excess,  that  is,  enough  of  them  must  be  added  to 
precipitate  the  total  quantity  of  the  metals  of  one  group,  before  it  is  possible 
to  test  for  metals  of  the  next  group.  Suppose,  for  instance,  a  solution  to  con- 
tain a  salt  of  bismuth  only.  Upon  the  addition  of  hydrogen  sulphide  to  the 
acidified  solution,  a  dark-brown  precipitate  (of  bismuth  sulphide)  is  produced, 
indicating  the  presence  of  a  metal  of  the  lead  group.  Suppose,  further,  that 
hydrogen  sulphide  has  not  been  added  in  sufficient  quantity  to  precipitate  the 
whole  of  the  bismuth,  then  ammonium  sulphide,  as  the  next  group-reagent, 
would  produce  a  further  precipitation  in  the  filtrate,  which  fact  would  lead  to 
the  assumption  that  a  metal  of  the  iron  group  was  present,  which,  however, 
would  not  be  the  case. 

If  the  solution  contain  but  one  metal,  the  group-reagents  are  added 
successively  in  small  quantities  to  the  same  solution,  until  the  reagent 
is  found  which  causes  a  precipitation,  which  reagent  is  then  added  in 
somewhat  larger  quantity  in  order  to  produce  a  sufficient  amount  of 
the  precipitate  for  further  examination. 

Acidifying1  the  solution.  Hydrosulphuric  acid  has  to  be  added 
to  the  acidified  solution  for  two  reasons,  viz.  :  In  a  neutral  or  alkaline 
solution  some  metals  of  the  arsenic  group  (which  are  to  be  pre- 
cipitated) would  not  be  precipitated  by  hydrogen  sulphide ;  some  of 
the  metals  of  the  iron  group  (which  are  not  to  be  precipitated)  would 
be  thrown  down. 

The  best  acid  to  be  used  in  acidifying  is  dilute  hydrochloric  acid ; 
but  this  acid  forms  insoluble  compounds  with  a  few  of  the  metals  of 
the  lead  group,  causing  them  to  be  precipitated.  Completely  pre- 
cipitated by  hydrochloric  acid  are  mercurous  and  silver  compounds ; 
partially  precipitated  are  compounds  of  lead,  chloride  of  lead  being 
somewhat  soluble  in  water.  The  precipitate  formed  by  hydrochloric 
acid  may  be  examined  by  Table  III.,  page  238. 

Hydrochloric  acid  added  to  a  solution  may,  in  a  few  cases  (other 
than  those  just  mentioned),  cause  a  precipitate,  as,  for  instance,  when 
added  to  solutions  containing  certain  compounds  of  antimony  or  bis- 
muth (the  precipitated  oxychlorides  of  these  metals  are  soluble  in 
excess  of  the  acid),  to  metallic  oxides  or  hydroxides  which  have  been 
dissolved  by  alkali  .hydroxides  (for  instance,  hydroxide  of  zinc  dis- 
solved in  potassium  or  ammonium  hydroxide),  to  solutions  of  alkali 
silicates,  when  silica  separates,  etc. 


SEPARATION  OF  METALS  INTO  DIFFERENT  GROUPS.       235 


Addition  of  hydrogen  sulphide.  This  reagent  is  employed 
either  in  the  gaseous  state  (by  passing  it  through  the  heated  solution) 
or  as  hydrogen  sulphide  water.  The  latter  reagent  answers  in  those 
cases  where  but  one  metal  is  present ;  if,  however,  metals  of  the 
arsenic  and  lead  groups  are  to  be  separated  from  metals  of  other 
groups,  the  gas  must  be  used. 


FIG.  26. 


FIG.  27. 


Apparatus  for  generating  hydro- 
gen sulphide. 


Apparatus  for  generating  hydro- 
gen sulphide. 


For  generating  hydrogen  sulphide  the  directions  given  on  page  107  may 
be  followed.  In  place  of  the  apparatus  there  mentioned  for  generating  the 
gas,  others  may  be  used  which  have  the  advantage  to  the  analyst  that  the 
supply  of  gas  may  be  better  regulated.  Fig.  26  shows  such  an  apparatus  for 
the  continuous  preparation  of  the  gas.  It  consists  of  three  glass  bulbs ;  the 
upper  bulb,  prolonged  by  a  tube  reaching  to  the  bottom  of  the  lowest  one,  is 
ground  air-tight  into  the  neck  of  the  second.  Ferrous  sulphide  is  introduced 
into  the  middle  bulb  through  the  tubulure,  which  is  then  closed  by  a  perforated 
cork  through  which  connection  is  made  with  the  wash-bottle.  Acid  poured  in 
through  the  safety  tube,  runs  into  the  bottom  globe  and  rises  to  the  ferrous 
sulphide  in  the  second  bulb.  Upon  closing  the  delivery  tube,  the  pressure  of 
the  generated  gas  forces  the  liquid  from  the  second  bulb  through  the  lower  to 
the  upper,  thus  preventing  contact  of  acid  and  ferrous  sulphide  until  the  gas  is 
used  again. 

A  convenient  and  cheaper  apparatus  is  shown  in  Fig.  27.  A  glass  tube, 
drawn  at  its  lower  end  to  a  small  point  and  partly  filled  with  pieces  of  ferrous 
sulphide,  is  suspended  through  a  cork  (not  air-tight)  in  a  cylinder  containing 
the  acid.  The  gas  supply  is  regulated  by  closing  or  opening  the  stop-cock,  and 
also  by  raising  or  lowering  the  tube  in  the  acid. 


236 


ANALYTICAL  CHEMISTRY. 


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SEPARATION  OF  METALS  INTO  DIFFERENT  GROUPS.       237 

In  some  cases  sulphur  is  precipitated  on  the  addition  of  hydrogen 
sulphide,  while  a  change  in  color  may  take  place.  This  change  is 
due  to  the  deoxidizing  action  of  hydrogen  sulphide,  the  hydrogen  of 
this  reagent  becoming  oxidized  and  converted  into  water,  while  sul- 
phur is  liberated.  Thus,  brown  ferric  compounds  are  converted  into 
pale-green  ferrous  compounds;  red  solutions  of  acid  chromates 
become  green;  and  red  permanganates  or  green  manganates  are 
decolorized. 

The  same  deoxidizing  action  of  hydrogen  sulphide  is  the  reason 
why  this  reagent  cannot  be  employed  in  a  solution  containing  free 
nitric  acid,  which  latter  compound  oxidizes  the  hydrogen  sulphide. 

Separation  of  the  metals  of  the  arsenic  from  those  of  the  lead 
group.  The  precipitate  produced  by  hydrogen  sulphide  in  acid  solu- 
tion contains  the  metals  of  the  arsenic  and  lead  groups.  They  are 
separated  by  means  of  ammonium  sulphide,  which  dissolves  the  sul- 
phides of  the  arsenic  group,  but  does  not  act  on  those  of  the  lead 
group. 

Addition  of  ammonium  sulphide.  This  reagent  should  never 
be  added  to  the  acid  solution,  but  the  solution  should  be  previously 
supersaturated  by  ammonium  hydroxide,  as,  otherwise,  a  precipitate 
of  sulphur  may  be  formed.  The  yellow  ammonium  sulphide  is 
almost  invariably  a  polysulphide  of  ammonium,  that  is,  ammonium 
sulphide  which  has  combined  with  one  or  more  atoms  of  sulphur.  If 
an  acid  be  added  to  this  compound,  an  ammonium  salt  is  formed, 
hydrogen  sulphide  is  liberated,  and  sulphur  precipitated : 

(NHJ2S2  -f  2HC1  =  2NH4C1  -f-  H2S  +  S. 

Ammonium  sulphide  precipitates  the  metals  of  the  iron  group  as 
sulphides,  with  the  exception  of  chromium,  which  is  precipitated  as 
hydroxide ;  aluminum  is  precipitated  in  the  same  form  of  combina- 
tion. 

Ammonium  sulphide  (or  ammonium  hydroxide)  causes  also  the 
precipitation  of  metallic  salts  which  have  been  dissolved  in  acids,  as, 
for  instance,  of  the  phosphates,  borates,  silicates,  or  oxalates  of  the 
alkaline  earths,  magnesium,  and  others.  The  processes  by  which  the 
nature  of  some  of  these  precipitates  is  to  be  recognized  are  found  in 
Table  VI.,  page  240. 

Addition  of  ammonium  carbonate.  The  reagent  used  is  the 
commercial  salt,  dissolved  in  water,  to  which  some  ammonia  water 


238  ANALYTICAL  CHEMISTRY. 

has  been  added.     Heating  facilitates  complete  precipitation  of  the 
carbonates  of  the  alkaline  earths. 


34.    SEPARATION  OF  THE  METALS  OF  EACH  GROUP. 
TABLE  III.— Treatment  of  the  precipitate  formed  by  hydrochloric  acid. 

The  precipitate  may  contain  silver,  mercurous,  and  lead  chlorides.     Boil 
the  washed  precipitate  with  much  water,  and  filter  while  hot. 


Filtrate  may  contain  lead 
chloride.     Add  dilute 
sulphuric  acid  ;  a  white 
precipitate  of  lead  sul- 
phate is  produced. 

Residue  may  consist  of  mercurous  and  silver  chlor- 
ides.    Digest  residue  with  ammonia  water. 

Solution  may  contain  sil-  i  A   dark    gray  residue  indi- 
ver.      Neutralize   with       cates  mercury,  the  white 
nitric  acid,  when  silver       mercurous  chloride  having 
chloride    is    re-precipi-       been  con  verted  into  di-mer- 
tated.                                        curous  ammonium  chloride. 

Treatment  of  the  precipitate  formed  by  hydrogen  sulphide  in 
warm  acid  solution.  The  precipitate  is  collected  upon  a  small 
filter,  well  washed  with  water,  and  then  examined  for  its  solubility 
in  ammonium  sulphide.  This  is  done  by  placing  a  portion  of  the 
washed  precipitate  in  a  test-tube,  adding  ammonium  sulphide,  and 
warming  gently.  It  is  either  wholly  insoluble  (metals  of  the  lead 
group),  and  treated  according  to  Table  IV.,  or  fully  soluble  (metals 
of  the  arsenic  group),  and  treated  according  to  Table  V.,  or  it  is 
partly  soluble  and  partly  insoluble  (metals  of  both  groups).  In  the 
latter  case,  the  total  quantity  of  the  washed  precipitate  is  to  be 
treated  with  warm  ammonium  sulphide;  upon  filtering,  an  insoluble 
residue  is  left,  which  is  treated  according  to  Table  IV. ;  to  the  fil- 

QUESTIONS. — 321.  State  the  three  groups  of  heavy,  and  the  three  groups  of 
light  metals.  322.  By  which  two  reagents  may  all  heavy  metals  be  precipi- 
tated ?  323.  Why  is  a  solution  acidified  before  the  addition  of  hydrogen  sul- 
phide, when  testing  for  metals?  324.  Which  metals  are  precipitated  by 
hydrochloric  acid?  325.  Which  two  groups  of  metals  are  precipitated  by 
hydrogen  sulphide  in  acid  solution?  326.  How  are  the  sulphides  of  the 
arsenic  group  separated  from  those  of  the  lead  group  ?  327.  Why  is  an  acid 
solution  neutralized  or  supersaturated  by  ammonium  hydroxide,  before  adding 
ammonium  sulphide  ?  328.  Which  two  groups  of  metals  are  precipitated  by 
ammonium  sulphide,  and  in  what  forms  of  combination?  329.  Name  the 
group-reagent  for  the  alkaline  earths.  330.  Which  metals  may  be  left  in  solu- 
tion after  hydrogen  sulphide,  ammonium  sulphide,  and  ammonium  carbonate 
have  been  added  ? 


SEPARATION  OF  THE  METALS  OF  EACH  GROUP. 


239 


trate,  dilated  sulphuric  acid  is  added  as  long  as  a  precipitate  is 
formed,  which  precipitate  contains  the  metals  of  the  arsenic  group  as 
sulphides,  generally  with  some  sulphur  from  the  ammonium  sulphide. 


TABLE  IV.— Treatment  of  that  portion  of  the  hydrogen  sulphide 
precipitate  which  is  insoluble  in  ammonium  sulphide. 

The  precipitate  may  contain  the  sulphides  of  lead,  copper,  mercury, 
bismuth,  and  cadmium.  Heat  the  well-washed  precipitate  with  nitric  acid  in 
a  test-tube,  and  filter. 


Residue    may  con- 
consist  of: 
Mercuric  sulph- 
ide,    which     is 
black   and   easily 
dissolves  in  nitro- 
hydrochloricacid, 
which      solution, 
after        sufficient 
evaporation,       is 
tested    by    potas- 
sium iodide,  etc. 
Lead  sulphate  is 
white,      pulveru- 
lent, and   soluble 
in    ammonium 
tartrate. 
Sulphur  is  yellow 
and  combustible. 

Filtrate  may  contain  the  nitrates  of  lead,  copper,  bis- 
muth, and  cadmium.     Add  to  the  solution  a  few  drops 
of  dilute  sulphuric  acid. 

Precipitated  is 
lead,  as  white 
lead   sulphate 
which  is  solu- 
ble in   ammo- 
nium   tart-rate 
with  excess  of 
ammonium 
hydroxide. 

Solution    may  contain  copper,  bismuth, 
and  cadmium.     Supersaturate  with  am- 
monium hydroxide. 

Precipitated  is 
white     bis- 
muth    hy- 
droxide. 
Dissolve     in 
hydrochloric 
acid  and  ap- 
ply tests  for 
bismuth. 

Solution  may  contain  copper 
and  cadmium. 
Divide  solution  in  two   parts, 
and  test  for  copper  by  potas- 
sium   ferrocyanide    in     the 
acidified  solution  ;  a  red  pre- 
cipitate   indicates  copper. 
To   second   part  add   potas- 
sium   cyanide    and     hydro- 
sulphuric   acid.      A    yellow 
precipitate    indicates    cad- 
mium. 

TABLE  V.— Treatment  of  the  hydrogen  sulphide  precipitate  which  is 
soluble  in  ammonium  sulphide. 


The  precipitate  may  contain  the  sulphides  of  arsenic,  antimony,  tin, 
and  a  few  of  those  metals  which  are  but  rarely  met  with  in  qualitative  analysis, 
such  as  gold,  platinum,  molybdenum,  and  others,  which  latter  metals,  if 
suspected,  may  be  detected  by  special  tests. 

Boil  the  washed  precipitate  with  strong  hydrochloric  acid. 


An  insoluble  yellow  residue  consists 
of  arsenous  sulphide 

The  residue  is  dissolved  by  boiling 
with  hydrochloric  acid  and  a  little 
potassium  chlorate,  and  the  solu- 
tion examined  by  Fleitmann's 
test. 

A  dark-colored  residue  may  indi- 
cate gold  or  platinum,  for  which 
use  special  tests. 


The  solution  may  contain  the  chlorides  of 
antimony  and  tin. 

The  solution  is  introduced  into  Marsh's  appara- 
tus when  all  antimony  is  gradually  evolved 
as  antimoniuretted  hydrogen,  while  tin  re 
mains  with  the  undissolved  zinc  as  a  black 
metallic  powder,  which  may  be  collected, 
washed,  dissolved  in  hydrochloric  acid,  and 
the  solution  tested  by  the  special  tests  for 
tin. 


240 


ANALYTICAL  CHEMISTRY. 


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SEPARATION  OF  THE  METALS  OF  EACH  GROUP.  241 

The  precipitation  of  sulphur,  in  the  absence  of  metals  of  the  arsenic  group, 
frequently  leads  beginners  to  the  assumption  that  metals  of  this  group  are 
present.  The  precipitate  consisting  only  of  sulphur  is  white  and  milky,  but 
flocculent,  and  more  or  less  colored  in  the  presence  of  the  metals  of  the 
arsenic  group. 

TABLE  VII. — Treatment  of  the  precipitate  formed  by  ammonium 

carbonate. 

The  precipitate  may  contain  the  carbonates  of  barium,  calcium,  and 
strontium.1  Dissolve  the  precipitate  in  acetic  acid,  and  add  potassium  dichromate. 


Precipitated  is 
barium,  as 
pale  yellow 
barium 
chromate. 

Solution  may  contain  calcium  and  strontium.     Neutralize 
solution  with  ammonia  water  and  add  potassium  chromate. 

Precipitated    is    stron- 
tium,  as  pale    yellow 
strontium'chromate. 

Solution  may  contain  calcium      Add 
ammonium  oxalate:  a  white  precipi- 
tate indicates  calcium. 

TABLE  VIII.— Detection  of  the  alkalies  and  of  magnesium. 

The  fluid  which  has  been  treated  with  hydrochloric  acid,  hydrogen  sulphide,  am- 
monium hydroxide,  sulphide,  and  carbonate,  may  contain  magnesium  and  the 
alkalies. 

Divide  solution  into  two  portions. 

To  the  first  portion  add  sodium  phosphate.  A  white  crystalline  precipitate  indi- 
cates magnesium.2 

The  second  portion  is  evaporated  to  dryness,  further  heated  (or  ignited)  until  all 
ammonium  compounds  are  expelled,  and  white  fumes  are  no  longer  given  off.  The 
residue  is  dissolved  in  water,  and  sodium  cobaltic  nitrite  added.  A  yellow  precipitate 
indicates  potassium.  The  residue  is  also  examined  by  flame  test :  a  yellow  color 
indicating  sodium,  a  red  color  lithium. 

Ammonium  compounds  have  to  be  tested  for  in  the  original  fluid  by  treating 
it  with  calcium  hydroxide,  when  ammonia  gas  is  liberated 


1  If  an  insufficient  quantity  of  ammonium  chloride  should  have  been  present,  some  magnesia 
may  also  be  contained  in  this  precipitate,  and  may  be  redissolved  by  treating  it  with  ammonium 
chloride  solution. 

2  If  an  insufficient  quantity  of  ammonium  chloride  has  been  produced  in  the  original  solution 
by  the  addition  of  hydrochloric  acid  and  ammonium  hydroxide,  a  portion  of  the  magnesia  may 
have  been  precipitated  by  the  ammonium  hydroxide  or  carbonate. 


QUESTIONS. — 331.  By  what  tests  can  mercurous  chloride  be  distinguished 
from  the  chloride  of  silver  or  lead  ?  332.  How  can  it  be  proved  that  a  pre- 
cipitate produced  by  hydrogen  sulphide  in  an  acid  solution  contians  a  metal 

16 


242  ANALYTICAL  CHEMISTRY. 

35.    DETECTION  OF  ACIDS. 

General  remarks.  There  are  no  general  methods  (similar  to  those 
for  the  separation  of  metals)  by  which  all  acids  can  be  separated,  first 
into  different  groups,  and  afterward  into  the  individual  acids.  It  is, 
moreover,  impossible  to  render  all  acids  soluble  (when  in  combination 
with  certain  metals)  without  decomposition,  as,  for  instance,  in  the 
case  of  carbonic  acid  when  in  combination  with  calcium ;  calcium 
carbonate  is  insoluble  in  water,  and  when  the  solution  is  attempted 
by  means  of  acids,  decomposition  takes  place  with  liberation  of  carbon 
dioxide.  Many  other  acids  suffer  decomposition  in  a  similar  manner, 
when  attempts  are  made  to  render  soluble  the  substances  in  which 
they  occur. 

It  is  due  to  these  facts  that  a  complete  separation  of  all  acids  is 
not  so  easily  accomplished  as  the  separation  of  metals.  There  is, 
however,  for  each  acid  a  sufficient  number  of  characteristic  tests  by 
which  it  may  be  recognized  ;  moreover,  the  preliminary  examination, 
as  well  as  the  solubility  of  the  substance,  and  the  nature  of  the  metal 
or  metals  present,  will  aid  in  pointing  out  the  acid  or  acids  which 
are  present. 

If,  for  instance,  a  solid  substance  be  completely  soluble  in  water, 
and  if  the  only  metal  found  were  iron,  it  would  be  unnecessary  to 
test  for  carbonic,  phosphoric,  and  hydrosulphuric  acids,  because  the 
combinations  of  these  acids  with  iron  are  insoluble  in  water  ;  there 
might,  however,  be  present  sulphuric,  hydrochloric,  nitric,  and  many 
other  acids,  which  form  soluble  salts  with  iron. 

Detection  of  acids  by  means  of  the  action  of  strong-  sulphuric 
acid  upon  the  dry  substance.  The  action  of  sulphuric  acid  upon 
a  dry  powdered  substance  often  furnishes  such  characteristic  indica- 


or  metals  of  either  the  arsenic  or  lead  group  ?  333.  How  can  mercuric  sul- 
phide be  separated  from  the  sulphides  of  copper  and  bismuth?  334.  How 
does  ammonium  hydroxide  act  on  a  solution  containing  bismuth  and  copper  ? 
335.  State  the  action  of  strong,  hot  hydrochloric  acid  on  the  sulphides  of 
arsenic  and  antimony.  336.  Suppose  a  solution  to  contain  salts  of  iron, 
aluminum,  zinc,  and  manganese ;  by  what  process  could  these  four  metals  be 
separated  and  recognized  ?  337.  How  can  barium,  calcium,  and  strontium  be 
recognized  when  dissolved  together  ?  338.  By  what  tests  is  magnesium  recog- 
nized ?  339.  State  a  method  of  separating  potassium  when  mixed  with  other 
metallic  compounds.  340.  How  are  ammonium  compounds  recognized  when 
in  solution  with  other  metals  ? 


DETECTION  OF  ACIDS.  243 

tions  of  the  presence  or  absence  of  certain  acids,  that  this  treatment 
should  never  be  omitted  when  a  search  for  acids  is  made. 

When  the  substance  under  examination  is  liquid,  a  portion  should 
be  evaporated  to  dryness,  and,  if  a  solid  residue  remains,  it  should 
be  treated  in  the  same  manner  as  a  solid. 

Most  non-volatile,  organic  substances  (including  most  organic 
acids)  color  sulphuric  acid  dark  when  heated  with  it. 

Dry  inorganic  salts  when  heated  with  sulphuric  acid  either  are 
decomposed,  with  liberation  of  the  acid  (which  may  escape  in  the 
gaseous  state),  or  with  liberation  of  volatile  products  (produced  by 
the  decomposition  of  the  acid  itself),  or  no  apparent  action  takes 
place.  See  Table  IX. 

Detection  of  acids  by  means  of  reagents  added  to  their 
neutral  or  acid  solution.  Whenever  a  substance  is  soluble  in 
water,  there  is  little  difficulty  of  finding  the  acid  by  means  of  Table 
X. ;  but  if  the  substance  is  insoluble  in  water,  and  has  to  be  rendered 
soluble  by  the  action  of  acids,  this  table  may,  in  some  cases,  be  of  no 
use,  because  the  acid  originally  present  in  the  substance  may  have 
been  liberated,  and  escaped  in  a  gaseous  state  (as,  for  instance,  when 
dissolving  insoluble  carbonates  in  acids),  or  the  tests  mentioned  in 
the  table  may  refer  to  neutral  solutions,  while  it  is  impossible  to 
render  the  solution  neutral  without  re-precipitating  the  dissolved 
acid.  If  calcium  phosphate,  for  instance,  be  dissolved  by  hydro- 
chloric acid,  the  magnesium  test  for  phosphoric  acid  cannot  be  used, 
because  this  test  can  be  applied  to  a  neutral  or  an  alkaline  solution 
only ;  in  attempting,  however,  to  neutralize  the  hydrochloric  acid 
solution,  calcium  phosphate  itself  is  re-precipitated. 

Table  XI.,  showing  the  solubility  or  insolubility  (in  water)  of  over 
300  of  the  most  important  inorganic  salts,  oxides,  and  hydroxides, 
will  greatly  aid  the  student  in  studying  this  important  feature.  It 
will  also  guide  him  in  the  analysis  of  inorganic  substances,  as  it  gives 
directions  for  over  300  (positive  or  negative)  tests  for  metals,  and  an 
equal  number  for  acids. 

To  understand  this,  it  must  be  remembered  that  any  salt  (or  oxide 
or  hydroxide)  which  is  insoluble  in  water  may  be  produced  and  pre- 
cipitated by  mixing  two  solutions,  one  containing  the  metal,  the  other 
containing  the  acid  of  the  insoluble  salt  to  be  formed.  For  instance  : 
Table  XI.  states  that  the  carbonates  of  most  metals  are  insoluble  in 
water.  To  produce,  therefore,  the  carbonate  of  any  of  these  metals 
(zinc,  for  instance)  it  becomes  necessary  to  add  to  any  solution  of 


244  ANALYTICAL  CHEMISTRY. 

zinc  (sulphate,  chloride,  or  nitrate  of  zinc)  any  soluble  carbonate 
(sodium  or  potassium  carbonate),  when  the  insoluble  zinc  carbonate 
is  produced. 

Soluble  carbonates  consequently  are  reagents  for  soluble  zinc  salts, 
while  at  the  same  time  soluble  zinc  salts  are  reagents  for  soluble 
carbonates. 

For  similar  reasons  soluble  zinc  salts  are,  according  to  Table  XI., 
reagents  for  soluble  phosphates,  arsenates,  arsenites,  hydroxides,  and 
sulphides,  but  not  for  iodides,  chlorides,  sulphates,  nitrates,  or 
chlorates. 

The  insolubility  of  a  compound  in  water  is  not  an  absolute  guide 
for  preparing  this  compound  according  to  the  general  rule  given 
above  for  the  precipitation  of  insoluble  compounds,  there  being  some 
exceptions. 

For  instance  :  Cupric  hydroxide  is  insoluble  in  water  ;  therefore, 
by  adding  solution  of  cupric  sulphate  to  any  soluble  hydroxide,  the 
insoluble  cupric  hydroxide  should  be  precipitated,  and  is  precipitated 
by  the  soluble  hydroxides  of  potassium  and  sodium,  but  not  perma- 
nently by  the  soluble  hydroxide  of  ammonium,  on  account  of  the 
formation  of  the  soluble  ammonium  cupric  sulphate. 

There  are  not  many  such  exceptions,  and  to  mention  them  in  the 
table  would  have  greatly  interfered  with  its  simplicity,  for  which 
reason  they  have  been  omitted. 

For  the  same  reason  some  compounds,  which  are  not  known  at  all, 
have  not  been  specially  mentioned.  For  instance,  according  to  Table 
XI.,  aluminum  carbonate  and  chromium  carbonate  are  insoluble  salts  : 
actually,  however,  these  compounds  can  scarcely  be  formed,  the 
affinity  between  the  weak  carbonic  acid  and  the  feeble  bases  not 
being  sufficient  to  unite  them. 

Finally,  it  may  be  stated  that  no  well-defined  line  can  be  drawn 
between  soluble  and  insoluble  substances.  There  is  scarcely  any 
substance  which  is  not  slightly  soluble  in  water,  and  many  of  the 
so-called  soluble  substances  are  but  very  sparingly  soluble,  as,  for 
instance,  the  hydroxide  and  sulphate  of  calcium. 

Table  XII.  shows  the  solubility  of  a  large  number  of  compounds 
more  accurately  than  Table  XL ;  it  may  be  used  for  reference. 


DETECTION  OF  ACIDS. 


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METHODS  FOR  QUANTITATIVE  DETERMINATIONS.         249 


36.    METHODS  FOR  QUANTITATIVE  DETERMINATIONS. 

General  remarks.  Quantitative  determination  of  the  different 
elements  or  groups  of  elements  may  be  accomplished  by  various 
methods,  Avhich  differ  generally  with  the  nature  of  the  substance  to 
be  examined.  But  even  one  and  the  same  substance  may  often  be 
analyzed  quantitatively  by  entirely  different  methods,  of  which  the 
two  principal  ones  are  the  gravimetric  and  volumetric  methods. 

In  the  gravimetric  method,  the  quantities  of  the  constituents  of  a 
substance  are  determined  by  separating  and  weighing  them  either  as 
such,  or  in  the  form  of  some  compound  the  exact  composition  of 
which  is  known.  For  instance :  From  cupric  sulphate,  the  copper 
may  be  precipitated  as  such  by  electrolysis  and  weighed  as  metallic 
copper,  or  it  may  be  precipitated  by  sodium  hydroxide  as  cupric  oxide, 
CuO,  and  weighed  as  such.  Knowing  that  every  79.2  parts  by  weight 
of  cupric  oxide  contain  of  oxygen  16  parts  and  of  copper  63.2  parts, 
the  weight  of  copper  contained  in  the  cupric  oxide  found  may  be 
readily  calculated. 

In  the  volumetric  method,  the  determination  is  accomplished  by  add- 
ing to  a  weighed  quantity  of  the  substance  to  be  examined,  a  solution 
of  a  reagent  of  a  known  strength  until  the  reaction  is  just  completed, 
no  excess  being  allowed.  For  instance :  We  know  that  every  80 
parts  by  weight  of  sodium  hydroxide  precipitate  79.2  parts  by  weight 
of  cupric  oxide,  containing  63.2  parts  by  weight  of  copper.  There- 
fore, if  we  add  a  solution  of  sodium  hydroxide  of  known  strength  to  a 
weighed  portion  of  cupric  sulphate  until  all  the  copper  is  precipitated, 

QUESTIONS.— 341.  Why  is  sulphuric  acid  added  to  a  solid  substance  when  it 
is  to  be  examined  for  acids  ?  342.  Mention  some  acids  which  cause  the  libera- 
tion of  colorless,  and  some  which  cause  the  liberation  of  colored  gases  when  the 
salts  of  these  acids  are  heated  with  sulphuric  acid.  343.  Mention  an  acid 
which  is  precipitated  by  barium  chloride  in  acid  solution,  and  some  acids  which 
are  precipitated  by  the  same  reagent  in  neutral  solution.  344.  Which  acids 
may  be  precipitated  by  silver  nitrate  from  neutral  solutions,  and  which  from 
either  neutral  or  acid  solutions  ?  345.  Mention  some  acids  which  form  soluble 
salts  only.  346.  Mention  three  soluble,  and  three  insoluble  carbonates,  phos- 
phates, arsenates,  sulphates,  and  sulphides  respectively.  347.  Which  oxides 
or  hydroxides  are  soluble,  and  which  are  insoluble  in  water  ?  348.  Mention 
some  metals,  the  solutions  of  which  are  precipitated  by  soluble  chlorides, 
iodides,  and  sulphides.  349.  State  a  general  rule  according  to  which  most 
insoluble  salts  may  be  formed  from  two  other  compounds.  350.  Why  is  it 
sometimes  impossible  to  render  a  substance  soluble  in  order  to  test  for  the  acid 
in  the  solution  obtained  ? 


250  ANALYTICAL  CHEMISTRY. 

we  may  calculate  from  the  volume  of  soda  solution  used  the  weight  of 
sodium  hydroxide,  and  from  this  the  weight  of  copper  which  has  been 
precipitated.  The  operation  of  volumetric  analysis  is  termed  titration. 

Gravimetric  methods.  While  the  quantitative  determinations  by 
these  methods  differ  widely  in  some  cases,  there  are  a  number  of  oper- 
ations so  often  and  so  generally  employed  that  a  few  remarks  may  be 
of  advantage  to  the  beginner.  A  small  quantity  (generally  from  0.5 
to  1  gramme)  of  the  substance  to  be  analyzed  is  very  exactly  weighed 
on  a  delicate  balance,  transferred  to  a  beaker,  and  dissolved  in  a  suit- 
able agent  (water  or  acid).  From  this  solution  the  constituent  to  be 

FIG.  28. 


Drying-oven. 

determined  is  precipitated  completely,  which  is  ascertained  by  allow- 
ing the  precipitate  to  subside  and  adding  to  the  clear  liquid  a  few 
drops  more  of  the  agent  used  for  precipitation.  The,  precipitate  is 
next  collected  upon  a  small  filter  of  good  filter  paper  containing  as 
little  of  inorganic  constituents  (ash)  as  possible ;  the  particles  of  pre- 
cipitate which  may  adhere  to  the  beaker  are  carefully  washed  off  by 
means  of  a  camel7 s-hair  brush.  The  precipitate  is  well  washed  (gen- 
erally with  pure  water)  until  free  from  adhering  solution,  and  dried 
by  placing  funnel  and  contents  in  a  drying-oven,  Fig.  28,  in  which  a 
constant  temperature  of  about  100°  C.  (212°  F.)  is  maintained.  The 
dried  filter  is  then  taken  from  the  funnel  and  its  contents  are  trans- 
ferred to  a  platinum  (or  porcelain)  crucible,  which  has  been  previously 


METHODS  FOR  Q  UANTITA  TIVE  DETEEMINA  TIONS.          251 

weighed  and  stands  on  a  piece  of  glazed,  colored  paper  in  order  to 
collect  any  particle  of  the  dried  precipitate  which  may  happen  to  fall 
beside  the  crucible.  The  filter,  from  which  the  precipitate  has  been 
removed  as  completely  as  possible,  by  slightly  rubbing  it,  is  now 
folded,  placed  upon  the  lid  of  the  crucible,  which  rests  on  a  triangle 
over  a  gas-burner,  and  completely  incinerated.  The  remaining  filter- 
ash,  with  particles  of  the  precipitate  mixed  with  it,  is  transferred  to 
the  crucible,  which  is  now  placed  over  the  burner  and  heated  until 
all  water  (or  possibly  other  substances)  is  completely  expelled.  After 
cooling,  the  crucible  is  weighed,  the  weight  of  the  empty  crucible  and 
that  of  the  filter-ash  (the  latter  having  been  previously  determined 
by  burning  a  few  filters  of  the  same  kind)  deducted,  and  thus  the 
quantity  of  the  precipitate  determined. 

As  platinum  crucibles  and  many  precipitates,  after  ignition,  absorb 
moisture  from  the  air,  it  is  well  to  allow  the  heated  crucible  to  cool 
in  a  desiccator.  This  is  a  closed  vessel  in  which  the  contained  air  is 
kept  dry  by  means  of  concentrated  sulphuric  acid.  Fig.  29  shows  a 
convenient  form  of  desiccator. 

The  empty  crucibles  should  be  weighed  under  the  same  conditions 
• — i.  e.,  after  having  been  heated  and  cooled  in  a  desiccator. 

PIG.  29.  FIG.  30. 


Desiccator.  Watch-glasses  for  weighing  filters. 


Some  precipitates  (as,  for  instance,  potassium  platinic  chloride), 
cannot  be  ignited  without  suffering  partial  or  complete  decomposition. 
It  is  for  this  reason  that  some  precipitates  are  collected  upon  filters 
which  have  been  previously  dried  at  100°  C.  (212°  F.)  and  weighed 
carefully.  The  precipitate  is  then  collected  upon  the  weighed  filter, 
well  washed,  dried  at  100°  C.  (212°  F.)  and  weighed. 

The  weighing  of  dried  filters  is  best  accomplished  by  placing  them 


252 


ANALYTICAL  CHEMISTRY. 


between  two  watch-glasses  held  together  by  means  of  a  brass  or  nickel 
clamp,  as  shown  in  Fig.  30. 

The  above-described  methods  may  be  employed  for  the  determina- 
tion of  those  substances  which  can  be  precipitated  from  their  solu- 
tions in  the  form  of  some  stable  compound.  Aluminum,  zinc,  iron, 
bismuth,  copper,  etc.,  may,  for  instance,  be  precipitated  as  hydroxides 
and  weighed  as  oxides,  into  which  the  precipitated  compound  is  con- 
verted by  ignition.  Sulphuric  acid  may  be  precipitated  and  weighed 
as  barium  sulphate,  phosphoric  acid  may  be  precipitated  by  magnesia 
mixture  and  weighed  as  magnesium  pyrophosphate,  etc.  Some  sub- 
stances, like  nitric  acid,  chloric  acid,  etc.,  cannot  be  precipitated  from 
their  solutions,  for  which  reason  other  methods  have  to  be  employed 
for  their  determination. 

FIG.  32. 


FIG.  31. 


10CC 


Liter  flask. 


Pipettes. 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.          253 

Volumetric  methods.  The  great  advantage  of  volumetric  over 
gravimetric  analysis  consists  chiefly  in  the  rapidity  with  which  these 
determinations  are  performed.  Unfortunately,  volumetric  methods 
cannot  be  employed  to  advantage  for  the  estimation  of  all  substances. 

The  special  apparatus  required  for  volumetric  analysis  consists  of 
a  few  flasks,  some  pipettes,  burettes,  and  a  burette-holder.  The  flasks 
should  have  a  mark  on  the  neck,  indicating  a  capacity  of  100,  250, 
500,  and  1000  c.c.  respectively.  (See  Fig.  31.) 


FIG.  33. 


FIG.  34. 


Mohr's  burette  and  clamp. 


Mohr's  burette  and  holder. 


Of  pipettes  (Fig.  32)  are  mostly  used  those  having  a  capacity  of 
5,  10,  25,  and  50  cubic  centimeters. 

Of  burettes  many  different  forms  are  used ;  in  most  cases  Mohr's 
burette  (Figs.  33  and  34)  answers  all  requirements,  but  its  applica- 


254  ANALYTICAL  CHEMISTRY. 

tion  is  excluded  whenever  the  test  solution  is  chemically  affected  by 
rubber,  as  in  the  case  of  solutions  of  silver,  permanganate,  and  a  few 

other  substances.  For  such  solutions 
Mohr's  burette  with  glass  stopcock,  or 
Gay  Ltissac's  burette  (Fig.  35)  is  generally 
used. 


Standard  solutions.  The  test  solu- 
tions used  in  volumetric  analysis  are  ad- 
justed according  to  a  uniform  system,  so 
that  each  solution  contains  in  a  liter 
(1000  c.c.)  the  weight  of  one  atom  or  one 
molecule  of  the  active  reagent  expressed 
in  grammes.  This  rule  refers  to  all  cases 
of  univalent  elements  (Ag,  Cl,  I),  or 
monobasic  acids  (HC1,  HNO3),  or  monacid 
bases (KOH,NH4  OH).  In  case  a  bivalent 
element  (O,  S),  or  di-basic  acids  (H2SO4, 
H2C2O4),  or  diacid  bases  [Ca(OH)2],  are 
used  in  volumetric  solutions,  only  one- 
half  of  the  atomic  or  molecular  weight  in 
grammes  is  used  per  liter,  so  as  to  have  the 
saturating  or  neutralizing  power  the  same 
for  an  equal  number  of  cubic  centimeters 
of  univalent  and  bivalent  substances. 

To  illustrate  why  this  is  done,  if  we 
were   to   take    the   molecular   weight  of 
hydrochloric  acid,  36.4,  and  of  sulphuric 
acid,  98,  in  grammes,  diluted  to  1000  c.c., 
the   saturating   power   of  1    c.c.    of  the 
diluted  sulphuric  acid  would  be  equal  to 
that  of  2  c.c.  of  hydrochloric  acid  solution^ 
because  36.4  parts  by  weight  of  hydro- 
chloric acid  saturate  40  parts  by  weight  of  sodium  hydroxide,  and 
98  parts  by  weight  of  sulphuric  acid  saturate  80  parts  by  weight  of 
sodium  hydroxide. 

The  solutions  thus  obtained  are  known  as  normal  solutions.  For 
some  operations  these  normal  solutions  are  too  concentrated,  and  are 
diluted  to  one-tenth  of  their  strength,  and  are  then  called  deci- 
normal  solutions. 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.         255 

Normal  solutions  are  generally  designated  by  — ,  deci-normal  solu- 
tions  by  — ,  centi-normal  solutions  by  ^—;  solutions  containing 
10  100 

2 
twice  the  amount  are  designated  as  double  normal,    -;  half  the 

amount  semi-normal,  — • 

2t 

In  some  instances  volumetric  solutions  are  prepared  which  do  not 
belong  to  the  above  system  of  normal  solutions,  but  are  adjusted  to 
correspond  to  a  certain  unit  of  the  special  substance  they  are  to  act 
upon.  Such  solutions  are  called  empirical  solutions;  as  an  instance 
may  be  mentioned  Fehling's  solution,  used  for  the  determination 
of  sugar.  This  solution  is  so  adjusted  that  1  c.c.  decomposes  or 
indicates  0.005  gramme  of  grape-sugar. 

Different  methods  of  volumetric  determination.  Of  these  we 
have  at  least  three,  which  may  be  called  the  direct,  the  indirect,  and 
the  method  of  rest  or  residue. 

The  direct  methods  are  used  in  all  cases  in  which  the  quantities  of 
volumetric  solutions  can  be  added  until  the  reaction  is  complete :  for 
instance,  until  an  alkaline  substance  has  been  neutralized  by  an  acid, 
or  a  ferrous  salt  has  been  converted  into  a  ferric  salt  by  potassium 
permanganate,  etc. 

In  the  indirect  methods  one  substance,  which  canoot  well  be  deter- 
mined volumetrically,  is  made  to  act  upon  a  second  substance,  with 
the  result  that,  by  this  action,  an  equivalent  amount  of  a  substance 
is  generated  or  liberated,  which  may  be  titrated.  For  instance :  Per- 
oxides, chromic  and  chloric  acids  when  boiled  with  strong  hydro- 
chloric acid,  liberate  chlorine,  which  is  not  determined  directly,  but 
is  caused  to  act  upon  potassium  iodide,  from  which  it  liberates  the 
iodine,  which  may  be  titrated  with  sodium  thiosulphate. 

The  methods  of  residue  are  based  upon  the  fact  that  while  it  is  im- 
possible or  extremely  difficult  to  obtain  complete  decomposition 
between  certain  substances  and  reagents,  when  equivalent  quantities 
are  added  to  one  another,  such  a  complete  decomposition  is  accom- 
plished by  adding  an  excess  of  the  reagent,  which  excess  is  afterward 
determined  by  a  second  volumetric  solution.  For  instance:  Car- 
bonate of  calcium,  magnesium,  zinc,  etc.,  cannot  well  be  determined 
directly,  for  which  reason  an  excess  of  normal  acid  is  used  for  their 
decomposition,  this  excess  being  titrated  afterward  by  means  of  an 
alkali. 


256  ANALYTICAL  CHEMISTRY. 

Indicators.  In  all  cases  of  volumetric  determination  it  is  of  the 
greatest  importance  to  observe  accurately  the  completion  of  the  reac- 
tion. In  some  cases  the  final  point  is  indicated  by  a  change  in  color, 
as,  for  instance,  in  the  case  of  potassium  permanganate,  which  changes 
from  a  red  to  a  colorless  solution,  or  chromic  acid,  which  changes 
from  orange  to  green  under  the  influence  of  deoxidizing  agents.  In 
other  cases  the  determination  is  indicated  by  the  formation  or  cessa- 
tion of  a  precipitate,  and  in  yet  others  the  final  point  could  not  be 
noticed  with  precision  unless  rendered  visible  by  a  third  substance 
added  for  that  purpose. 

Such  substances  are  termed  indicators.  Litmus,  phenol-phtalein, 
methyl-orange,  etc.,  are  used  as  indicators  in  acidimetry  and  alka- 
limetry. Starch  paste  is  an  indicator  for  iodine,  potassium  chromate 
for  silver,  etc.  Of  indicators,  a  few  drops  are  in  most  cases  sufficient 
for  the  purpose. 

Litmus  solution.  This  is  made  by  exhausting  coarsely  powdered  litmus  with 
boiling  alcohol,  which  removes  a  red  coloring  matter,  erythrolitmin.  The 
residue  is  treated  with  about  an  equal  weight  of  cold  water,  so  as  to  dissolve 
the  excess  of  alkali  present  in  litmus.  The  remaining  mass  is  extracted  with 
about  five  times  its  weight  of  boiling  water,  and  filtered.  The  solution  should 
be  kept  in  wide-mouthed  bottles,  stoppered  with  loose  plugs  of  cotton  to  ex- 
clude dust  but  to  admit  air.  Blue  and  red  litmus  paper  is  made  by  impregnat- 
ing strips  of  unsized  white  paper  with  the  blue  solution  obtained  by  the  above 
process,  or  with  this  solution  after  just  enough  hydrochloric  acid  has  been 
added  to  impart  to  it  a  distinct  red  tint. 

Phenol-phtalein  solution.  1  gramme  of  phenol-phtalein  is  dissolved  in  100 
€  c.  of  diluted  alcohol.  The  colorless  solution  is  colored  deep  purplish-red  by 
alkali  hydrates  or  carbonates,  but  not  by  bicarbonates ;  acids  render  the  red 
solution  colorless.  The  solution  is  not  suitable  as  an  indicator  for  ammonia 
or  bicarbonates. 

Methyl-orange  solution.  1  gramme  of  methyl-orange  (also  known  as  helian- 
thin,  tropa3olin  D,  or  Poirier's  orange  III),  dimethylamido-azobenzol-sul- 
phonic  acid,  (CH3)2N.C6H4.N.NC6H4.SO3H,  is  dissolved  in  1000  c.c.  of  water. 
The  solution  is  yellow  when  in  contact  with  alkaline  hydrates,  carbonates,  or 
bicarbonates.  Carbonic  acid  does  not  affect  it,  but  mineral  acids  change  its 
color  to  crimson. 

Rosolic  acid  solution.  1  gramme  of  commercial  rosolic  acid  (chiefly  C20H16O3) 
is  dissolved  in  10  c.c  of  alcohol,  and  water  added  to  make  100  c.c.  The  solu- 
tion turns  violet-red  with  alkalies,  yellow  with  acids. 

Other  indicators  used  at  times  in  acidimetry  are  solutions  of  brazil-wood, 
cochineal,  corallin,  eosin,  fluorescein,  turmeric,  etc. 

Titration.  This  term  is  used  for  the  process  of  adding  the  volu- 
metric solution  from  the  burette  to  the  solution  of  the  weighed  sub- 
stance until  the  reaction  is  completed.  We  also  speak  of  the  standard 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.         257 

or  liter  of  a  volumetric  test-solution,  when  we  refer  to  its  strength 
per  volume  (per  liter  or  per  cubic  centimeter). 

Of  the  principal  processes  of  titration,  or  of  volumetric  methods 
used,  may  be  mentioned  those  based  upon  neutralization  (acidimetry 
and  alkalimetry),  oxidation  and  reduction  (permanganates  and  chro- 
mates  as  oxidizing,  oxalic  acid  and  ferrous  salts  as  reducing  agents) 
precipitation  (silver  nitrate  by  sodium  chloride),  and  finally  those 
which  depend  on  the  action  of  iodine  and  hyposulphite  (iodimetry). 

Acidimetry  and  alkalimetry.  Preparing  the  volumetric  test- 
solutions  is  often  more  difficult  than  to  make  a  volumetric  deter- 
mination. Whenever  the  reagents  employed  can  be  obtained  in  a 
chemically  pure  condition  it  is  an  easy  task  to  prepare  the  solution, 
because  a  definite  weight  of  the  reagent  is  dissolved  in  a  definite 
volume  of  water.  In  many  instances,  however,  the  reagent  cannot 
be  obtained  absolutely  pure,  and  in  such  cases  a  solution  is  made  and 
its  standard  adjusted  afterward  by  methods  which  will  be  spoken  of 
later. 

Neither  the  common  mineral  acids,  such  as  sulphuric,  hydro- 
chloric, and  nitric  acids,  nor  the  alkaline  substances,  such  as  sodium 
hydroxide  or  ammonium  hydroxide,  are  sufficiently  pure  to  permit  of 
being  used  directly  for  volumetric  solutions,  because  these  substances 
contain  water,  and  an  absolutely  correct  determination  of  the  amount 
of  this  water  is  an  operation  which  involves  a  knowledge  of  gravi- 
metric methods. 

It  is  for  this  reason  that  the  basis  in  preparing  a  volumetric  normal 
acid  solution  is  oxalic  acid,  a  substance  which  can  be  readily  obtained 
in  a  pure  crystallized  condition. 

Normal  acid  solution.  Crystallized  oxalic  acid  has  the  com- 
position H2C2O4.2H2O  and  a  molecular  weight  of  125.7.  Being 
dibasic,  only  half  of  its  weight  is  taken  for  the  normal  solution, 
which  is  made  by  placing  62.85  grammes  of  pure  crystallized  oxalic 
acid  in  a  liter  flask,  dissolving  it  in  pure  water,  filling  up  to  the 
mark  at  the  temperature  of  15°  C.  (59°  F.)  and  mixing  thoroughly. 

Normal  solutions  of  sulphuric  or  hydrochloric  acid  are,  for  various 
reasons,  often  preferred  to  oxalic  acid.  These  solutions  are  best 
made  by  diluting  approximately  the  acids  named,  titrating  the  solu- 
tion with  normal  sodium  hydroxide,  using  phenol-phtalein  as  an 
indicator,  and  adding  water  until  equal  volumes  saturate  one  another. 
For  instance,  if  it  should  be  found  that  10  c.c.  normal  alkali  solution 

17 


258  ANALYTICAL  CHEMISTRY. 

neutralize  7.6  c.c.  of  the  acid,  then  24  c.c.  of  water  have  to  be  added 
to  every  76  c.c.  of  the  acid  in  order  to  obtain  a  normal  solution. 
Normal  sulphuric  acid  contains  48.91  grammes  of  H2SO4,  and  normal 
hydrochloric  acid  36.37  grammes  of  HC1  per  liter. 

These  normal  solutions  can  be  made  conveniently  by  diluting  either  30  c.c. 
of  pure,  concentrated  sulphuric  acid  of  sp.  gr.  1.84,  or  130  c.c.  of  hydrochloric 
acid  of  sp.  gr.  1.16  to  1000  c.c.  The  solutions  thus  obtained  are  yet  too  con- 
centrated and  are  adjusted  as  described  above. 

Other  methods  of  determining  the  exact  standard  of  normal  acids  depend 
upon  the  precipitation  of  10  c.c.  of  the  sulphuric  acid  solution  by  barium 
chloride,  or  of  10  c.c.  of  the  hydrochloric  acid  solution  by  silver  nitrate,  and 
weighing  the  precipitated  barium  sulphate  or  silver  chloride.  Ten  c.c.  of 
normal  sulphuric  acid  give  1.1736  gramme  of  barium  sulphate,  and  10  c.c.  of 
normal  hydrochloric  acid  1.43  gramme  of  silver  chloride. 

A  third  method  depends  on  the  formation  of,  and  the  weighing  as,  an 
ammonium  salt.  Ten  c.c.  of  either  acid  are  neutralized  (or  slightly  super- 
saturated) with  ammonia  water.  The  solution  is  evaporated  in  a  previously 
weighed  platinum  dish  over  a  water-bath,  the  dry  salt  is  repeatedly  moistened 
with  alcohol,  and  finally  dried  in  an  air-bath  at  a  temperature  of  105°  C. 
(221°  F.)  for  about  half  an  hour.  Ten  c.c.  of  normal  sulphuric  acid  give  of 
ammonium  sulphate  0.6592  gramme,  and  10  c.c.  of  normal  hydrochloric  acid 
of  ammonium  chloride  0.5338  gramme. 

Normal  alkali  solution.  A  normal  solution  of  sodium  carbonate 
may  be  made  by  dissolving  52.92  grammes  (one-half  the  molecular 
weight)  of  pure  sodium  carbonate  (obtainable  by  heating  pure  sodium 
bicarbonate  to  a  low  red-heat)  in  water,  and  diluting  to  one  liter. 
This  solution,  however,  is  not  often  used,  but  may  serve  for  standard- 
izing acid  solutions,  as  it  has  the  advantage  of  being  prepared  from  a 
substance  that  can  be  easily  obtained  in  a  pure  condition,  which  is 
not  the  case  in  preparing  the  otherwise  more  useful  normal  solutions 
of  potassium  or  sodium  hydroxide,  both  of  which  substances  contain 
and  absorb  water. 

The  solutions  are  made  by  dissolving  about  60  grammes  of  potas- 
sium hydroxide  or  50  grammes  of  sodium  hydroxide  in  about  1000 
c.c.  of  water,  titrating  this  solution  with  normal  acid,  and  diluting  it 
with  water,  until  equal  volumes  of  both  solutions  neutralize  one 
another  exactly. 

The  indicators  used  in  alkalimetry  are  chiefly  solution  of  litmus 
or  phenol  phtalein,  only  a  few  drops  of  either  solution  being  needed 
for  a  determination. 

Whenever  carbonates  are  titrated  with  acids,  or  vice  versa,  the 
solution  has  to  be  boiled  towaid  the  end  of  the  reaction  in  order  to 


METHODS  FOE  QUANTITATIVE  DETERMINATIONS.         259 

drive  off  the  carbon  dioxide,  as  neither  of  the  two  indicators  men- 
tioned gives  reliable  results  in  the  presence  of  carbonic  acid  or  an 
acid  carbonate.  This  boiling  is  unnecessary  when  methyl- orange  is 
used,  because  it  is  not  influenced  by  carbonic  acid. 

FIG.  36. 


Titration. 

The  proper  mode  of  performing  the  operation  of  titration  is  shown 
in  Fig.  36. 

When  salts  of  organic  acids  with  alkali  metals  are  to  be  titrated  with  normal 
acids,  these  salts  are  first  converted  into  carbonates.  This  is  accomplished  by 
igniting  the  weighed  quantity  of  the  salt  in  a  crucible  of  porcelain  or  platinum. 
The  chemical  action  which  takes  place  during  the  ignition  of  potassium  acetate 
may  be  shown  thus  : 

2KC2H302  +  80  =  K2CO3  +  3H2O  +  3CO2. 

In  a  similar  manner  the  alkali  salts  of  all  organic  acids  are  converted  into 
carbonates.  Frequently  some  carbon  is  left  unburned  ;  this,  however,  does  not 
interfere  with  the  result  of  the  titration.  The  titration  is  made  with  the  liquid 
obtained  by  dissolving  in  water  the  residue  left  after  ignition. 

Neutralization  equivalents.  The  normal  solutions  of  acid  and 
alkali  may  be  used  for  the  determination  of  a  large  number  of  sub- 
stances, either  directly  (as  in  the  case  of  free  acids,  caustic  and  alka- 
line carbonates  and  bicarbonates)  or  indirectly  (as  in  the  case  of  salts 
of  most  of  the  organic  acids,  with  alkalies,  which  are  first  converted 
into  carbonates  by  ignition). 


260  ANALYTICAL  CHEMISTRY. 

One  c.c.  of  normal  acid  is  the  equivalent  of : 

Gramme. 

Ammonia,  NH3        .        . .  0.01701 

Ammonium  carbonate,  (NH4)2CO3 0.04293 

Ammonium  carbonate  (U.  S.  P.),  NH^HCOg.NH^NHaCOjj     .        .  0.05226 

Lead  acetate,  crystallized  Pb(C2H3O2)2.3H2O1         ....  0.18900 

Lead  subacetate,  Pb2O(C2H3O2)2 1 0.13662 

Lithium  benzoate,  LiC7H5O2  2 0.12772 

Lithium  carbonate,  Li2CO3  2 0.03693 

Lithium  citrate,  Li3C6H5O7  2 0.06986 

Lithium  salicylate,  LiC7H5O3  2 0.14368 

Potassium  acetate,  KC2H3O2  2 0.09789 

Potassium  bicarbonate,  KHCO3 0.09988 

Potassium  bitartrate,  KHC4H4O6  2 0.18767 

Potassium  carbonate,  K2CO3 0.06895 

Potassium  citrate,  crystallized,  K3C6H5OrH2O  2     .  0.10789 

Potassium  hydroxide,  KOH 0.05599 

Potassium  permanganate,  KMnO4  3 '    .  0.03153 

Potassium  sodium  tartrate,  KNaC4H4O6.4H2O  2      .  0.14075 

Potassium  tartrate,  2K2C4H4O6.H2O  2 0.11734 

Sodium  acetate,  NaC2H3O2.3H2O  2  . 0.13574 

Sodium  benzoate,  NaC7H5O2  2 0.14371 

Sodium  bicarbonate,  ISTaHCO3 0.08385 

Sodium  borate,  crystallized,  Na2B4O7.10H2O 0.19046 

Sodium  carbonate,  crystallized,  Na2CO3.10H2O        ....  0.14272 

Sodium  carbonate,  Na2CO3 0.05292 

Sodium  hydroxide,  NaOH .  0  03996 

One  c.c.  of  normal  sodium   carbonate,  potassium  hydroxide,  or 
sodium  hydroxide,  is  the  equivalent  of: 

Gramme. 

Acetic  acid,  HC2H3O2 0.05986 

Citric  acid,  crystallized,  H3C6H5O7.H2O 0.06983 

Hydrobromic  acid,  HBr 0.08076 

Hydrochloric  acid,  HC1  . 0.03637 

Hydriodic  acid,  HI 0.12753 

Hypophosphorous  acid,  HPH2O2 0.06588 

Lactic  acid,  HC3H5O3 0.08989 

Nitric  acid,  HNO3 0.06289 

Oxalic  acid,  crystallized,  H2C2O4.2H2O 0.06285 

Phosphoric  acid,  H3PO4  (to  form  K2HPO4 ;  with  phenol-phtalein)  0.04890 

Phosphoric  acid,  H3PO4  (to  form  KH2PO4;  with  methyl-orange)  0.09780 

Potassium  dichromate,  K2Cr2O7  (with  phenol-phtalein)         .        .  0  14689 

Sulphuric  acid,  H2SO4 0.04891 

Tartaric  acid,  H2C4H4O6 0.07482 

Oxidimetry.     Potassium  permanganate.     The  substances  gen- 
erally used  as   oxidizing  agents  are  potassium  permanganate  and 

1  With  sulphuric  acid  and  methyl-orange. 

2  After  ignition.  3  With  oxalic  acid  only. 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.          261 

potassium  dichr ornate,  both  of  which  salts  can  be  obtained  in  a  pure 
crystallized  condition. 

Potassium  permanganate,  KMnO4  =  157.67,  acts  generally  in  the 
presence  of  free  acids,  upon  deoxidizing  substances,  by  losing  5  atoms 
of  oxygen  of  the  8  atoms  contained  in  two  molecules,  as  is  shown  in 
the  following  equations : 

2KMn04  +    5H2C204  +  3H2SO4  =  K2SO4  -f  2MnSO4  +  10CO2         +  8H2O. 
2KMn04  +  10FeS04    +  8H2SO4  =  K2SO4  +  2MnSO4  +    5Fe23SO4  +  8H2O. 

It  follows,  that  two-fifths  of  the  molecular  weight  of  potassium 
permanganate,  or  63.068  grammes,  are  the  equivalent  of  1  oxygen 
atom.  But'as  oxygen  is  diatomic  and  the  volumetric  normal  is  cal- 
culated for  monatomic  values,  this  number  must  be  divided  by  2, 
and  31.534  grammes  of  pure  crystallized  potassium  permanganate  is 
therefore  the  amount  to  furnish  1  liter  of  normal  solution,  but  as  this 
is  too  concentrated  for  most  determinations,  a  deci-normal  solution 
containing  3.1534  grammes  to  the  liter  is  generally  employed. 

Permanganate  solution,  when  recently  made,  without  observing 
certain  precautions,  will  deteriorate  for  a  certain  length  of  time,  i.  e., 
until  all  traces  of  organic  and  other  deoxidizing  matters  have  become 
oxidized  by  the  permanganate. 

In  order  to  prepare  permanent  volumetric  solutions  of  perman- 
ganate it  is  advisable  to  make  two  solutions,  one  too  concentrated  and 
the  other  too  dilute  for  standard.  These  solutions  are  boiled  and  set 
aside  in  well-closed  bottles  for  two  days,  in  order  to  allow  any  pre- 
cipitated matter  to  settle.  By  mixing  the  two  solutions  in  the  proper 
proportions  a  solution  of  the  desired  strength  can  be  obtained,  and 
as  there  is  no  longer  any  matter  in  the  solution  which  can  act 
decomposingly  upon  the  permanganate  the  solution  retains  its  stand- 
ard for  many  months. 

To  prepare  the  two  solutions  necessary  for  deci-normal  potassium 
permanganate  solution,  dissolve  3.5  grammes  of  potassium  perman- 
ganate and  3  grammes  in  one  liter  of  water  each.  Boil  the  solutions 
for  a  few  minutes,  set  them  aside  for  two  days,  and  pour  off  the  clear 
portions  of  each  solution  into  separate  vessels  provided  with  glass 
stoppers. 

To  find  the  proportions  in  which  these  solutions  have  to  be  mixed 
in  order  to  obtain  a  deci  normal  solution  the  strength  of  each  one  has 
to  be  determined  ;  this  is  done  as  follows  :  To  a  mixture  of  10  c.c. 
of  deci-normal  oxalic  acid  solution  and  1  c.c.  of  concentrated  sulphuric 
acid,  while  yet  hot,  is  added  from  a  burette  the  weaker  permanganate 


262  ANALYTICAL  CHEMISTRY. 

solution  until  it  is  no  longer  decolorized.     In  the  same  manner  the 
titer  of  the  stronger  solution  is  determined. 

Having  ascertained  the  strength  of  each  solution,  the  proportions 
for  mixing  them  are  ascertained  by  using  the  formula: 

Stronger  solution.  Weaker  solution. 

(W— 10)  S.        +        (10-S.)  W. 

By  W  are  indicated  the  c.c.  of  weaker  solution,  by  S  the  c.c.  of 
stronger  solution  required  to  decompose  10  c.c.  of  deci-normal  oxalic 
acid. 

For  instance:  Assuming  that  9.5  c.c.  of  the  stronger  (S)  and  10.4 
c.c.  of  the  weaker  (W)  solution  had  been  required,  then,  substituting 
these  values  in  the  above-given  formula,  we  obtain  : 

(10.4—10)  9.5  +  (10—9.5)  10.4, 
or 

3.8        -f        5.2, 

making  9  c.c.  of  final  solution. 

The  bulk  of  the  two  solutions  is  now  mixed  in  the  same  proportion, 
say  380  c.c.  of  the  stronger  and  520  c.c.  of  the  weaker  solution 

After  the  mixture  is  thus  prepared,  a  new  trial  should  be  made, 
when  equal  volumes  of  the  solution  prepared  and  of  deci-normal 
oxalic  acid  solution  should  exactly  decompose  one  another.  Instead 
of  working  with  10  c.c.  of  the  solutions  it  is  advisable  to  use  larger 
quantities,  say  20  or  even  50  c.c.,  whereby  the  errors  made  by  reading 
are  diminished. 

Instead  of  using  oxalic  acid  for  standardizing  permanganate  solution, 
metallic  iron  may  be  used,  and  the  operation  should  be  conducted  as  follows : 
0.2  gramme  of  pure,  thin  iron  wire  is  dissolved  in  about  20  c.c.  of  dilute  sul- 
phuric acid  (1  acid,  5  water)  by  the  aid  of  heat,  and  in  a  flask  arranged  a& 
in  Fig.  37.  The  flask  is  provided,  by  means  of  a  perforated  cork,  with  a 
piece  of  glass  tubing,  to  which  is  attached  a  piece  of  rubber  tubing  in  which 
is  cut  a  vertical  slit  about  one  inch  long  and  which  is  closed  at  the  upper 
end  by  a  piece  of  glass  rod ;  gas  or  steam  generated  in  the  flask  may  escape, 
while  atmospheric  air  cannot  enter,  the  ferrous  solution  being  thus  protected 
from  oxidation. 

The  iron  solution,  obtained  from  the  0.2  gramme  of  iron,  is  cooled  and 
diluted  with  about  300  c.c.  of  water,  and  then  deci-normal  potassium  perman- 
ganate solution  is  added  with  constant  stirring  until  the  solution  is  tinged 
pinkish. 

As  1  c.c.  of  deci-normal  permanganate  solution  corresponds  to  0.005588 
gramme  of  metallic  iron,  the  0.2  gramme  of  iron  wire  used  will  consume  3'5.7 
c.c.  of  the  solution. 

Permanganate  is  often  used  in  determinations  of  iron  and  iron  compounds. 
Many  of  the  latter  contain  iron  in  the  ferric  state,  which  must  be  converted 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.          263 

into  ferrous  compounds  before  titration.  This  conversion  is  accomplished  by 
heating  the  solution  of  a  weighed  quantity  of  the  ferric  compound  with  nascent 
hydrogen— i.  e.,  with  metallic  zinc  and  dilute  sulphuric  acid — in  a  flask 
arranged  as  the  one  spoken  of  above,  and  shown  in  Fig.  37. 

FIG.  37. 


Flask  for  dissolving  iron  for  volumetric  determination. 

A  very  much  quicker  reduction  of  the  ferric  into  a  ferrous  compound  may  be 
accomplished  by  adding  very  slowly  with  constant  stirring  a  saturated  solution 
of  sodium  sulphite  to  the  boiling,  acidified  iron  solution  contained  in  the  flask 
until  the  liquid  becomes  colorless.  All  excess  of  sulphur  dioxide  is  expelled 
before  titrating,  by  boiling  the  solution  (which  should  contain  a  sufficient 
quantity  of  hydrochloric  acid  to  decompose  all  sodium  sulphite)  for  about  ten 
minutes  in  a  flask,  arranged  as  the  one  mentioned  above. 

One  c.c.  of  deci-normal  potassium  permanganate,  containing  of  this 
salt  0.0031534  gramme,  is  the  equivalent  of: 

Gramme. 

Amyl  nitrite,  CgH^NO.j 0.003153 

Barium  dioxide,  BaO2 0.058390 

Calcium  hypo-phosphite,  Ca(PH2O2)2 0.002121 

Ethyl  nitrite,  C2H5NO2 0.037435 

Ferric  hypophosphite,  Fe2(PH2O2)6 0.002088 

Ferrous  ammonium  sulphate,  Fe(NH4)2(SO^2.6H2O    .        .        .  0.039130 

Ferrous  carbonate,  FeCO3 0.011573 

Ferrous  oxide,  FeO 0.007195 

Ferrous  sulphate,  FeSO4 0.015170 

Ferrous  sulphate,  crystallized,  FeSO4.7H2O 0  027742 

Hydrogen  dioxide,  H2O2  (see  explanation,  page  84)     .        .        .  0.001696 

Hypophosphorous  acid,  HPH2O2 0.001647 

Iron,  in  ferrous  compounds,  Fe 0  005588 

Oxalic  acid,  crystallized,  H2C2O4.2H2O         .        .        .        .        .  0.006285 

Oxygen,  O 0.000798 

Potassium  hypophosphite,  KPH2O2 0.002598 

Potassium  nitrite,  KNO2       .        .         .        .        .        .        .        .  0.042480 

Sodium  hypophosphite,  NaPH2O2.H2O 0.002646 

Sodium  nitrite,  NaNO2 0.034465 


264  ANALYTICAL  CHEMISTRY. 

Potassium  dichromate,  K2Cr2O7  =  293.78.  Whenever  this  salt 
acts  in  the  presence  of  free  acid,  as  an  oxidizing  agent,  it  transfers  3 
atoms  of  oxygen  upon  the  deoxidizing  agent,  thus  : 

K2Cr207  +  GFeSO,  +  7H2SO4  =  K2SO4  +  Cr2(SO4)3  +  7H2O  +  3[Fe2(SO4)3]. 

A  normal  solution  should,  therefore,  contain  one-sixth  of  the  molec- 
ular weight,  or  48.963  grammes  per  liter.  For  most  purposes  a 
deci-normal  solution  is  preferred,  and  this  is  made  by  dissolving 
4.8963  grammes  of  pure  potassium  dichromate  in  a  sufficient  quantity 
of  water  to  make  1000  c.c. 

The  disadvantage  of  this  solution  is,  that  the  final  point  of  titra- 
tion  cannot  be  well  seen,  for  which  reason,  in  the  determination  of 
iron,  for  which  it  is  chiefly  used,  the  end  of  the  reaction  is  determined 
by  the  method  of  spotting,  i.  e.,  by  taking  out  a  drop  of  the  solution 
and  testing  it  on  a  white  porcelain  plate  with  a  drop  of  freshly  pre- 
pared potassium  ferricyanide  solution ;  when  this  no  longer  gives  a 
blue  color,  the  reaction  is  at  an  end. 

In  all  determinations  by  this  solution  dilute  sulphuric  acid  has  to 
be  added,  because  both  the  potassium  and  chromium  require  an  acid 
to  combine  with,  as  shown  in  the  above  equation. 

The  titration  equivalents  of  this  solution  for  ferrous  salts  are  the 
same  as  those  of  deci-normal  potassium  permanganate  solution. 

lodimetry.  Solutions  of  iodine  and  of  sodium  thiosulphate  (hypo- 
sulphite) act  upon  one  another  with  the  formation  of  sodium  iodide 
and  sodium  tetrathionate : 

21  +  2Na2S2O3  =  2NaI  +  Na2S4O6. 

A  normal  solution  of  one  can  be  standardized  by  a  normal  solution 
of  the  other.  As  indicator  is  used  starch  solution,  which  is  colored 
blue  by  minute  portions  of  free  iodine. 

Starch  solution  is  made  by  mixing  1  gramme  of  starch  with  10  c.c.  of  cold 
water,  and  then  adding  enough  boiling  water,  under  constant  stirring,  to  make 
about  200  c.c.  of  a  transparent  jelly.  If  the  solution  is  to  be  preserved  for  any 
length  of  time,  10  grammes  of  zinc  chloride  should  be  added. 

Many  other  substances,  such  as  sulphurous  acid,  hydrogen  sulphide, 
arsenous  oxide,  act  upon  iodine  with  the  formation  of  colorless  com- 
pounds, and  may,  therefore,  be  estimated  by  normal  solution  of  iodine, 
while  the  iodine  may  be  standardized  by  the  thiosulphate  solution. 
In  many  cases  the  latter  solution  is  also  used  for  the  determination  of 
chlorine,  which  is  caused  to  act  upon  potassium  iodide,  the  liberated 
iodine  being  titrated. 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.         265 

Deci-normal  iodine  solution  is  the  one  generally  used,  and  is  made 
by  dissolving  12.653  grammes  of  pure  iodine  in  a  solution  of  18 
grammes  of  potassium  iodide  in  about  300  c.c.  of  water,  diluting  the 
solution  to  1000  c.c. 

To  the  article  to  be  estimated  by  this  solution  is  added  a  little  starch 
solution,  and  then  the  iodine  solution  until,  on  stirring,  the  blue  color 
ceases  to  be  discharged. 

Many  substances,  such  as  sulphurous  acid  and  its  salts,  hydrogen  sulphide, 
arsenous  oxide,  etc.,  are  acted  upon  by  iodine  in  such  a  manner  that  this 
element  enters  into  combination  with  constituents  of  the  compounds  named. 
The  quantity  of  iodine  thus  taken  up  forms  the  basis  for  calculating  the  quan- 
tity of  the  substance  acted  upon. 

In  the  case  of  arsenous  oxide  the  titration  is  made  in  alkaline  solution. 
Arsenous  oxide  and  sodium  bicarbonate  are  dissolved  in  water,  and  this  solu- 
tion, containing  sodium  met-arsenite,  is  titrated  with  iodine  solution,  when 
sodium  met-arsenate  and  sodium  iodide  are  formed : 

NaAsO2  4  21  4  2NaHCO3  =  NaAsO3  +  2NaI  +  H2O  +  2CO2. 

When  sulphurous  acid,  sulphites,  or  acid  sulphites  are  titrated  with  iodine  the 
addition  of  an  alkali  is  unnecessary  ;  the  action  is  this : 

H2S  4-      21  =  2HI        +  S. 
H2SO3  4-  21  4-  H2O  =  H2S04    -f  2HI. 
Na^SOg  4  21  4-  H2O  =  Na.2SO4  -f  2HL 

In  the  titration  of  antimony  and  potassium  tartrate  by  iodine  an  alkaline  solu- 
tion is  required,  and  for  this  reason  sodium  bicarbonate  is  added  to  the  solution. 
The  reaction  which  takes  place  is  somewhat  doubtful,  but  the  following  equa- 
tion, even  if  not  absolutely  correct,  corresponds  to  the  quantities  of  the  substances 
acting  upon  one  another : 

2KSbOC4H4O6  +  H2O  +  41  +  4NaHCO3  = 
2HSbO3  +  2KHC4H406  4  4NaI  +  4CO2  -f  H2O. 

One  c.c.  of  deci-normal  iodine  solution,  containing  of  iodine 
0.012653  gramme,  is  the  equivalent  of: 

Gramme. 

Antimony  and  potassium  tartrate,  2KSbOC4H4O6.H2O          .        .  0.016560 

Arsenous  oxide,  As2O3 0.004942 

Hydrogen  sulphide,  H28 0.001699 

Potassium  sulphite,  crystallized,  K2SO3.2H2O        ....  0.009692 

Sodium  bisulphite,  NaHSO3 0.005193 

Sodium  hyposulphite  (thiosulphate),  Na2S2O3.5H2O     .        .        .  0.024764 

Sodium  sulphite,  crystallized,  Na2SO3.7H2O  .        .  .        .  0.012579 

Sulphur  dioxide,  SO2 0.003195 

Sodium  thiosulphate  (Hyposulphite).  The  crystallized  salt, 
Na2S2O3.5H2O  =  247.64,  is  used  for  making  the  deci-normal  solution 
by  dissolving  24.764  grammes  of  the  pure  crystallized  salt  in  water 
to  make  1000  c.c.  If  the  salt  should  not  be  absolutely  pure,  a  some- 


266  ANALYTICAL  CHEMISTRY. 

what  larger  quantity  (30  grammes)  should  be  dissolved  in  1000  c.c. 
of  water,  and  this  solution  titrated  with  deci-normal  solution  of 
iodine  and  diluted  with  a  sufficient  quantity  of  water  to  obtain  the 
deci-normal  solution. 

The  article  to  be  tested,  containing  free  iodine,  either  in  itself  or 
after  the  addition  of  potassium  iodide,  is  treated  with  this  solution 
until  the  color  of  iodine  is  nearly  discharged,  when  a  little  starch 
liquor  is  added,  and  the  addition  of  the  solution  continued  until  the 
blue  color  has  just  disappeared. 

The  titration  of  iron  in  ferric  salts  by  hyposulphite  is  based  on 
the  liberation  of  iodine  from  potassium  iodide  by  all  ferric  salts  : 
Fe2Cl6  -f  2KI  =  2FeCl2  -f  2KC1  +  21. 

The  reaction  shown  in  the  above  equation  requires  a  temperature 
of  40°  to  50°  C.  (104°  to  122°  F.),  and  at  least  half  an  hour's  time 
to  make  sure  of  its  completion.  The  digestion  should  be  performed 
in  a  closed  flask.  If  iron  be  present  in  combination  with  organic 
acids,  the  addition  of  some  hydrochloric  acid  becomes  necessary. 
Before  titration  the  solution  is  allowed  to  cool,  and  the  titration 
should  be  promptly  finished,  as  otherwise  errors  by  re-oxidation  of 
the  ferrous  salt  may  be  made. 

One  c.c.  of  deci-normal  solution  of  sodium  thiosulphate,  containing 
of  the  crystallized  salt  0.024764  gramme,  is  the  equivalent  of: 

Gramme. 

Bromine,  Br 0.007976 

Chlorine,  Cl 0.003537 

Iodine,  I 0.012653 

Iron,  Fe,  in  ferric  salts 0.005588 

Deci-normal  bromine  solution  (Koppeschaar's  solution).  The 
great  volatility  of  bromine,  even  from  aqueous  solutions,  interferes 
very  much  with  the  stability  of  volumetric  solutions.  For  this 
reason  a  solution  is  prepared  which  does  not  contain  free  bromine, 
but  an  alkali  bromide  and  bromate,  from  which,  by  addition  of  an 
acid,  a  definite  quantity  of  bromine  (7.976  grammes  per  liter)  may 
be  liberated  when  required.  The  chemical  change  is  this : 
5NaBr  +  NaBrO3  +  «HC1  =  6NaCl  -f-  3H2O  -f-  6Br. 

As  the  bromine  salts  are  rarely  chemically  pure,  a  solution  is  made 
which  is  stronger  than  necessary  and  is  then  adjusted  to  the  titer  of 
hyposulphite  solution. 

The  solution  is  prepared  as  follows :  Dissolve  3  grammes  of  sodium 
bromate,  and  50  grammes  of  sodium  bromide  (or  3.2  and  50  grammes 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.          267 

of  the  potassium  salts)  in  900  c.c.  of  water.  Of  this  solution,  which 
is  too  concentrated,  transfer  20  c.c.  into  a  bottle  of  about  250  c.c. 
provided  with  a  glass  stopper.  Next  add  75  c.c.  of  water,  5  c.c.  of 
pure  hydrochloric  acid,  and  immediately  insert  the  stopper.  Shake 
the  bottle  a  few  times  to  cause  the  liberation  of  bromine,  then  quickly 
introduce  1  gramme  of  potassium  iodide,  taking  care  that  no  bromine 
vapor  escape.  Gradually  an  equivalent  quantity  of  iodine  is  liber- 
ated from  the  potassium  iodide  by  the  bromine.  When  this  has  taken 
place  add  to  the  contents  of  the  flask  a  little  starch  solution  and  from 
a  burette  deci-normal  hyposulphite  solution  until  the  blue  color  has 
been  discharged. 

The  use  of  bromine  solution  is  directed  by  the  U.  S.  P.  in  one  case  only,  viz., 
for  the  volumetric  determination  of  phenol  (carbolic  acid).  This  substance 
forms  with  bromine  tribromphenol  and  hydrobromic  acid : 

C6H5OH  +  6Br  =  C6H2Br3OH  +  3HBr. 

The  molecular  weight  of  phenol  is  93.78,  and  as  it  reacts  with  6  atoms  of 
bromine,  one-sixth  of  93.78,  or  15.63  grammes  of  phenol  correspond  to  one  liter 
of  normal,  and  1.563  grammes  of  deci-normal  bromine  solution ;  i.  e.,  1  c.c.  of 
deci-normal  bromine  solution  corresponds  to  0.001563  gramme  of  phenol.  The 
U.  S.  P.  directs  the  assay  to  be  made  as  follows:  Dissolve  1.563  gramme  of  the 
specimen  in  water  to  make  1  liter.  Transfer  25  c.c.  of  this  solution  (0.0391 
phenol)  to  a  glass  stoppered  bottle  of  about  200  c.c.  capacity,  and  add  30  c.c.  of 
deci-normal  bromine  solution  and  5  c.c.  of  hydrochloric  acid.  Shake  the  con- 
tents of  the  bottle  repeatedly,  during  half  an  hour,  then  quickly  introduce  1 
gramme  of  potassium  iodide,  allow  the  reaction  to  take  place  and  titrate  the 
solution  with  deci-normal  hyposulphite,  as  described  above.  Deduct  the  num- 
ber of  c.c.  of  hyposulphite  used  from  the  30  c.c.  of  bromine  solution.  The 
remainder  multiplied  by  4  indicates  the  percentage  of  phenol  in  the  carbolic 
acid  examined. 

Deci-normal  solution  of  silver.  The  pure,  dry  crystallized 
silver  nitrate,  AgNO3  =  169.55,  is  used  for  this  solution,  which  is 
made  by  dissolving  16.955  grammes  of  the  salt  in  water  to  make 
1000  c.c.  The  standard  of  this  solution  may  be  found  by  means  of 
a  deci-uormal  solution  of  sodium  chloride  containing  of  this  salt 
5.837  grammes  in  one  liter. 

Volumetric  silver  solution  is  used  directly  for  the  estimation  of 
most  chlorides,  iodides,  bromides,  and  cyanides,  including  the  free 
acids  of  these  salts.  Insoluble  chlorides  must  first  be  converted  into 
a  soluble  form  by  fusing  them  with  sodium  hydroxide,  dissolving  the 
fused  mass  (containing  sodium  chloride)  in  water,  filtering  and  neu- 
tralizing with  nitric  acid. 

The  hydroxides  and  carbonates  of  alkali  metals  and  of  alkaline 


268  ANALYTICAL  CHEMISTRY. 

earths  may  be  converted  into  chlorides  by  evaporation  to  dryness 
with  pure  hydrochloric  acid,  and  heating  to  about  120°  C.  (248°  F.). 
The  chlorides  thus  obtained  may  be  titrated  with  silver  solution. 

In  the  case  of  chlorides,  iodides,  and  bromides,  normal  potassium 
chromate  is  used  as  an  indicator.  This  salt  forms  with  silver  nitrate 
a  red  precipitate  of  silver  chromate,  but  not  before  the  silver  chloride 
(bromide  or  iodide)  has  been  precipitated  entirely.  In  case  free  acids 
are  determined  by  silver,  these  are  neutralized  with  sodium  hydroxide 
before  titration. 

The  operation  is  conducted  as  follows :  The  weighed  quantity  of 
the  chloride  is  dissolved  in  50-100  c.c.  of  water,  neutralized  if  neces- 
sary, mixed  with  a  little  potassium  chromate,  and  silver  solution 
added  from  the  burette  until  a  red  coloration  is  just  produced,  which 
does  not  disappear  on  shaking. 

In  estimating  cyanides,  the  operation  can  be  conducted  as  above 
described,  or  it  can  be  modified,  use  being  made  of  the  formation  of 
soluble  double  cyanides  of  silver  and  an  alkali  metal.  The  reaction 
takes  place  thus : 

2KCN  +  AgNO3  =  AgK(CN)2  +  KNTO3. 

If  to  this  soluble  double  compound  more  silver  nitrate  be  added,  it 

is  decomposed  with  the  formation  of  a  precipitate  of  silver  cyanide : 

AgK(CN)a  +  AgNO3  ==  2AgCN  +  KNO3. 

The  estimation  of  hydrocyanic  acid  or  of  simple  cyanides,  according  to  this 
method,  is  accomplished  by  first  rendering  slightly  alkaline  the  solution  of  the 
substance  to  be  examined  by  the  addition  of  sodium  hydroxide,  and  then 
adding  the  silver  solution  until  a  permanent  cloudiness  is  produced  in  the 
liquid,  which  shows  that  all  cyanogen  present  has  been  converted  into  the 
soluble  double  salt.  As  but  one-half  of  the  silver  solution  has  been  added 
which  is  needed  for  the  complete  conversion  of  the  cyanogen  present  into 
silver  cyanide,  the  number  of  c.c.  of  the  standard  silver  solution  employed 
will  indicate  exactly  one-half  of  the  equivalent  amount  of  cyanide  present  in 
the  solution. 

One  c.c.  of  deci-normal  silver  nitrate  solution,  containing  0.016955 
gramme  of  AgNO3,  is  the  equivalent  of: 

Gramme. 

Ammonium  bromide,  NH4Br       .                 0.009777 

Ammonium  chloride,  NH4C1 0.005338 

Ammonium  iodide,  NHJ 0.014454 

Calcium  bromide,  CaBr2 0.009971 

Ferrous  bromide,  FeBr2 0.010770 

Ferrous  iodide,  FeI2 0-015447 

Hydriodic  acid,  HI 0.012753 

Hydrobromic  acid,  HBr 0.008076 


METHODS  FOR  QUANTITATIVE  DETERMINATIONS.          269 

Gramme. 

Hydrochloric  acid,  HC1 0.003637 

Hydrocyanic  acid,  HCN,  to  first  formation  of  precipitate     .         .  0.005396 

Hydrocyanic  acid,  HCN,  with  indicator      .         .         .         .         .  0.002698 

Lithium  bromide,  LiBr 0.008677 

Potassium  bromide,  KBr 0.011879 

Potassium  chloride,  KC1               0.007440 

Potassium  cyanide,  KCN,  to  first  formation  of  precipitate  .         .  0.013002 

Potassium  cyanide,  KCN,  with  indicator 0.006501 

Potassium  iodide,  KI 0.016556 

Potassium  sulphocyanate,  KCNS 0.009699 

Sodium  bromide,  NaBr 0.010276 

Sodium  chloride,  NaCl 0.005837 

Sodium  iodide,  Nal 0.014953 

Zinc  bromide,  ZnBr2             0.011231 

Zinc  chloride,  ZnCl2 0.006792 

Zinc  iodide,  ZnI2 0.015908 

Deci-normal  solution  of  sodium  chloride  is  made  by  dissolving 
5.837  grammes  of  pure  sodium  chloride  in  enough  water  to  make 
1000  c.c.  The  titration  is  made  in  neutral  solution,  normal  potas- 
sium chromate  being  used  as  an  indicator.  (See  explanation  in 
previous  paragraph  on  silver  solution.) 

One  c.c.  of  deci-normal  sodium  chloride  solution,  containing 
0.005837  gramme  of  NaCl,  is  the  equivalent  of: 

Gramme 

Silver,  Ag 0.010766 

Silver  nitrate,.  AgNO8 0.016955 

Silver  oxide,  Ag2O 0.011564 

Deci-normal  solution  of  potassium  sulphocyanate  ( Volhard's 
solution).  This  solution,  like  the  sodium  chloride  solution,  is  used 
as  a  companion  to  silver  nitrate ;  it  has  the  advantage  that  it  can  be 
used  in  acid  solutions,  with  ferric  ammonium  sulphate  (ferric  alum) 
as  indicator.  Silver  nitrate  forms  in  the  potassium  sulphocyanate  a 
white  precipitate  of  silver  sulphocyanate  : 

KCNS  +  AgNO3  =  AgCNS  +  KNO3. 

As  indicator  is  used  ferric  alum,  which  produces  with  sulpho- 
cyanate a  deep  brownish-red  color,  which,  however,  does  not  appear 
permanently  until  all  silver  has  been  precipitated. 

As  potassium  sulphocyanate  is  rarely  pure,  10  grammes,  which  is 
about  3  per  cent,  more  than  the  quantity  required,  are  dissolved  in 
1000  c.c.  of  water.  This  solution  has  to  be  adjusted  by  standardizing 
with  deci-normal  silver  solution  until  equal  volumes  decompose  one 
another  exactly. 


270  ANALYTICAL  CHEMISTRY. 

The  sulphocyanate  solution  is  used  in  the  determination  of  the 
amount  of  ferrous  iodide  in  the  saccharated  salt  and  in  the  syrup. 

The  operation  is  performed  thus  :  To  the  solution  of  the  ferrous 
iodide  are  added  nitric  acid,  ferric  alum,  and  of  deci-normal  silver 
nitrate  solution  a  quantity  more  than  sufficient  to  convert  all  iodine 
into  silver  iodide.  The  excess  of  silver  nitrate  present  in  the  mix- 
ture is  determined  by  sulphocyanate  solution. 

The  titration  equivalents  of  this  solution  for  silver  are  the  same 
as  those  of  deci-normal  sodium  chloride. 

Gas-analysis.  The  analysis  of  gases  is  generally  accomplished  by  measur- 
ing gas  volumes  in  graduated  glass  tubes  (eudiometers)  over  mercury  (in  some 
cases  over  water),  noting  carefully  the  pressure  and  temperature  at  which  the 
volume  is  determined. 

From  gas  mixtures,  the  various  constituents  present  may  often  be  eliminated 
by  causing  them  to  be  absorbed  one  after  another  by  suitable  agents.  For 
instance :  From  a  measured  volume  of  a  mixture  of  nitrogen,  oxygen,  and 
carbon  dioxide,  the  latter  compound  may  be  removed  by  allowing  the  gas  to 
remain  in  contact  for  a  few  hours  with  potassium  hydroxide,  which  will  absorb 
all  carbon  dioxide,  the  diminution  in  volume  indicating  the  quantity  of  carbon 
dioxide  originally  present.  The  volume  of  oxygen  may  next  be  determined  by 
introducing  a  piece  of  phosphorus,  which  will  gradually  absorb  the  oxygen, 
the  remaining  volume  being  pure  nitrogen. 

In  some  cases  gaseous  constituents  of  liquids  or  solids  are  eliminated  and 
measured  as  gases.  Thus,  the  carbon  dioxide  of  carbonates,  the  nitrogen 
dioxide  evolved  from  nitrates,  the  nitrogen  of  urea  and  other  nitrogenous 
bodies,  are  instances  of  substances  which  are  eliminated  from  solids  in  the 
gaseous  state  and  determined  by  direct  measurement. 

The  gas  volume  thus  found  is,  in  most  cases,  converted  into  parts  by  weight. 
The  basis  of  this  calculation  is  the  weight  of  1  c.c.  of  hydrogen,  which,  at  the 
temperature  of  0°  C.  (32°  F.)  and  a  pressure  of  760  mm.,  is  0.0000896  gramme. 
1  c.c.  of  any  other  gas  weighs  as  many  more  times  as  the  molecule  of  this 
substance  is  heavier  than  that  of  hydrogen.  Thus  the  molecular  weight  of 
carbon  dioxide  is  22  times  greater  than  that  of  hydrogen,  consequently  1  c.c. 
of  carbon  dioxide  weighs  22  times  heavier  than  1  c.c.  of  hydrogen,  or  0.0019712 
gramme. 

It  has  been  shown  on  pages  21  and  25  that  heat  and  pressure  cause  a  regular 
increase  or  decrease  in  volume.  The  data  there  given  are  used  in  calculating 
the  volume  of  the  measured  gas  for  the  temperature  of  0°  C.  (32°  F. )  and  a 
pressure  of  760  m.m. 

Methods  of  gas-analysis  have  been  adopted  by  the  U.  S.  P.  in  the  quantita- 
tive determination  of  amyl  nitrite  and  ethyl  nitrite.  The  operation  is  per- 
formed in  an  apparatus  known  as  a  nitrometer,  consisting  of  two  glass  tubes  held 
in  upright  position  and  connected  at  the  lower  ends  by  a  piece  of  rubber 
tubing.  One  of  the  tubes  is  open,  the  other  one  is  graduated  and  provided 
with  a  glass  stopcock  near  the  upper  end.  In  using  the  nitrometer  for  the 
analysis  of  ethyl  nitrite  the  graduated  tube  is  filled  with  saturated  solution  of 


DETECTION  OF  IMPURITIES.  271 

sodium  chloride,  in  which  nitrogen  dioxide  is  almost  insoluble.  Next  are 
introduced  through  the  stopcock  the  measured  (or  weighed)  quantity  of  ethyl 
nitrite  with  a  sufficient  amount  of  solution  of  potassium  iodide  and  sulphuric 
acid.  By  the  action  of  these  agents  nitrogen  dioxide  is  liberated,  and  from  the 
volume  obtained  the  quantity  of  nitrite  present  is  calculated.  The  decom- 
position is  shown  by  the  equation  : 

C2H5N02  +  KI  +  H2SO4  =  C2H5OH  +  I  +  KHSO4  +  NO. 


37.    DETECTION  OF  IMPURITIES  IN  OFFICIAL  INORGANIC 
CHEMICAL  PREPARATIONS. 

General  remarks.  Very  little  has  been  said,  heretofore,  about 
impurities  which  may  be  present  in  the  various  chemical  prepara- 
tions, and  this  omission  has  been  intentional,  because  it  would  have 
increased  the  bulk  of  this  book  beyond  the  limits  considered  neces- 
sary for  the  beginner. 

Impurities  present  in  chemical  preparations  are  either  derived  from 
the  materials  used  in  their  manufacture,  or  they  have  been  intention- 
ally added  as  adulterations.  In  regard  to  the  last,  no  general  rule 
for  detecting  them  can  be  given,  the  nature  of  the  adulterating  article 
varying  with  the  nature  of  the  substance  adulterated  ;  the  general 


QUESTIONS.— 351.  Explain  the  principles  which  are  made  use  of  in  gravi- 
metric and  volumetric  determinations.  352.  Give  an  outline  of  the  operations 
to  be  performed  in  the  gravimetric  determination  of  copper  in  cupric  sulphate. 

353.  What  are  normal  and  deci-normal  solutions,  and  how  are  they  made? 

354.  What  is  the  use  of  indicators  in  volumetric  analysis?    Mention  some 
indicators  and  explain  their  action.     355.  Why  is  oxalic  acid  preferred  in 
preparing  normal  acid  solution?     What  quantity  of  oxalic  acid  is  contained 
in  a  liter,  and  why  is  this  quantity  used  ?     356.  Suppose  2  grammes  of  crys- 
tallized sodium  carbonate  require  14  c.c.  of  normal  acid  for  neutralization: 
What  are  the  percentages  of  crystallized  sodium  carbonate  and  of  pure  sodium 
carbonate  contained  in  the  specimen  examined?    357.  Ten  grammes  of  dilute 
hydrochloric  acid  require  35.5  c.c.  of  normal  sodium  hydroxide  solution  for 
neutralization.    What  is  the  strength  of  this  acid  ?    358.  Explain  the  action 
of  potassium  permanganate  and  of  potassium  dichromate  when  used  for  volu- 
metric purposes.     359.  Which  substances  may  be  determined  volumetrically 
by  solutions  of  iodine  and  sodium  thiosulphate  ?     Explain  the  mode  in  which 
the  determinations  by  these  agents  are  accomplished.     360.  Suppose  1  gramme 
of  potassium  iodide  requires  for  titration  60  c.c.  of  deci-normal  solution  of 
silver  nitrate :  What  quantity  of  pure  potassium  iodide,  is  indicated  by  this 
determination?     361.  Describe  in  detail  the  volumetric  determination  of  car- 
bolic acid.     362.  For  what  purposes  is  potassium  sulphocyanate  used  volu- 
metrically, and  what  is  its  action?     363.  Explain  the  method  used  for  the 
analysis  of  ethyl  nitrite. 


272  ANALYTICAL  CHEMISTRY. 

properties  of  the  substance  to  be  examined  for  purity  will,  in  most 
cases,  suggest  the  nature  of  those  substances  which  possibly  may  have 
been  added,  and  for  them  a  search  has  to  be  made,  or,  if  necessary,  a 
complete  analysis,  by  which  is  proved  the  absence  of  everything  else 
but  the  constituents  of  the  pure  substance. 

Impurities  derived  from  the  materials  used  in  the  manufacture  of 
a  substance  (generally  through  an  imperfect  or  incorrect  process  of 
manufacture),  or  from  the  vessels  used  in  the  manufacture,  are  usually 
but  few  in  number  (in  any  one  substance),  and  their  nature  can,  in 
most  cases,  be  anticipated  by  one  familiar  with  the  process  of  manu- 
facture. For  one  not  acquainted  with  the  mode  of  preparation  it 
would  be  a  rather  difficult  task  to  study  the  nature  of  the  impurities 
which  might  possibly  be  present. 

The  same  remarks  apply  to  the  methods  by  which  the  impurities 
can  be  detected.  One  familiar  with  analytical  chemistry  can  easily 
find,  in  most  cases,  a  good  method  by  which  the  presence  or  absence 
of  an  impurity  can  be  demonstrated  ;  but  to  one  unacquainted  with 
chemistry  it  might  be  an  impossibility  to  detect  impurities,  even  if 
a  method  were  given. 

For  these  reasons  little  stress  has  been  laid  upon  the  occurrence  of 
impurities  in  the  various  chemical  preparations  heretofore  considered. 
Moreover,  the  U.  S.  P.  gives,  in  most  cases,  directions  for  the  detec- 
tion of  impurities,  so  explicit  that  anyone  acquainted  with  analytical 
operations  will  find  no  difficulty  in  performing  these  tests  satisfac- 
torily. 

However,  while  the  Pharmacopoeia  gives  exact  instructions  how  to 
manipulate,  it  furnishes  no  explanations  why  certain  methods  have 
been  adopted,  or  why  certain  operations  are  to  be  performed.  It  is 
for  this  reason,  and  for  the  special  benefit  of  the  beginner,  that  a  few 
paragraphs  are  devoted  to  the  consideration  of  official  methods  for 
testing  the  chemical  preparations  of  the  U.  S.  P. 

Official  chemicals  and  their  purity.  Absolute  purity  of  chemi- 
cals is  essential  in  some  cases,  as,  for  instance,  when  they  are  intended 
as  reagents ;  such  chemicals  are  commercially  designated  as  C.  P. 
(chemically  pure).  For  the  majority  of  medicinal  chemicals,  how- 
ever, such  absolute  purity  is  unnecessary,  as  the  small  proportion  of 
harmless  impurities  present  in  no  wise  interferes  with  the  therapeutic 
action  of  the  substance,  and  a  demand  for  absolute  purity,  which 
greatly  enhances  the  cost  of  chemicals,  is  therefore  unreasonable  and 
not  required  by  the  Pharmacopoeia. 


DETECTION  OF  IMPURITIES.  273 

The  presence  of  a  small  fraction  of  one  per  cent,  of  sodium  chloride 
in  many  official  chemicals  cannot  be  looked  upon  as  objectionable, 
while  the  same  amount  of  arsenic  would  render  the  preparation  unfit 
for  medicinal  use. 

The  methods  used  by  the  Pharmacopoeia  to  determine  the  quality 
of  a  chemical  preparation  may  be  divided  into  four  classes,  as  follows : 
1.  Tests  as  to  identity  ;  2.  Qualitative  tests  for  impurities ;  3.  Quan- 
titative tests  for  the  limit  of  impurities  ;  4.  Quantitative  determina- 
tion of  the  chief  constituent. 

Tests  as  to  identity.  These  tests  are  partly  of  a  physical,  partly 
of  a  chemical  character.  They  include,  in  the  physical  part,  the 
examination  of  the  appearance,  color,  crystalline  structure,  specific 
gravity,  fusing-point,  boiling-point,  etc. 

The  chemical  tests  given  are  sufficiently  characteristic  to  leave  no 
doubt  as  to  the  true  nature  or  identity  of  the  substance.  In  order  to 
accomplish  this  object  it  is  not  necessary  to  apply  all  the  analytical 
reagents  characteristic  of  the  substance  or  its  component  parts,  but 
the  U.  S.  P.  selects  from  the  often  large  number  of  known  tests  one, 
or  possibly  a  few,  which  answer  best  in  the  special  case. 

For  instance,  while  we  have  a  number  of  tests,  both  for  potassium 
and  iodine,  the  U.  S.  P.,  in  the  article  on  potassium  iodide,  gives  but 
one  reaction  for  each  of  these  elements.  Yet  these  tests  have  been 
selected  with  sufficient  judgment  to  admit  of  no  doubt  regarding  the 
nature  of  the  substance. 

Qualitative  tests  for  impurities.  These  tests  are  in  many  cases 
described  minutely,  i.  e.,  the  quantity  to  be  taken  of  both  the  sub- 
stance to  be  examined  and  the  reagent  to  be  added  is  stated.  More- 
over the  amount  of  solvent  (water,  acid,  etc.)  to  be  used  is  mentioned, 
and  other  details  are  given.  The  object  of  this  exactness  in  describ- 
ing the  tests  is  not  only  to  render  the  work  easy  for  one  not  fully 
familiar  with  analytical  methods,  but  also,  in  some  cases,  to  fix  a 
limit  for  the  admissible  quantity  of  an  impurity.  A  certain  reagent 
may,  in  a  concentrated  solution,  indicate  the  presence  of  a  trace  of 
an  impurity,  while  in  a  more  dilute  solution  this  reagent  will  fail  to 
detect  it.  The  selection  of  the  reagents  used  in  certain  tests  is  also 
made  with  the  view  of  establishing  a  sufficient  purity  for  pharmaco- 
poeial  purposes  of  the  article  examined  without  demanding  an  absolute 
purity. 

A  few  instances  may  help  to  illustrate  these  remarks  :  Potassium 

18 


274  ANALYTICAL  CHEMISTRY. 

can  be  precipitated  from  a  solution  of  its  salts  by  a  number  of  re- 
agents, which,  however,  differ  widely  in  sensitiveness.  Thus,  tartaric 
acid  will  cause  the  formation  of  a  precipitate  of  potassium  bitartrate 
in  a  solution  containing  at  least  0.1  per  cent,  of  potassium ;  in  solu- 
tions containing  a  less  amount  no  precipitate  is  formed.  Platinic 
chloride  is  somewhat  more  sensitive  than  tartaric  acid,  and  sodium 
cobaltic  nitrite,  which  is  still  more  delicate,  causes  a  precipitate  in 
solutions  containing  even  as  little  as  0.04  per  cent,  of  potassium.  It 
is  evident  that  by  using  either  one  or  the  other  of  the  three  reagents 
mentioned  for  the  detection  of  potassium,  this  metal  may  or  may  not 
be  found,  according  to  the  quantity  present  in  a  solution.  The 
Pharmacopoeia,  in  directing  the  use  of  one  of  these  reagents,  limits 
the  amount  of  a  permissible  quantity  of  potassium  according  to  the 
sensitiveness  of  the  reagent. 

Again,  in  testing  for  arsenic,  the  chemist  has  his  choice  between  a 
number  of  more  or  less  delicate  tests.  Gutzeit's  test  is  so  sensitive 
that  by  means  of  it  arsenic  can  be  detected  in  a  solution  containing 
only  0.000001  gramme  of  arsenous  oxide  in  a  cubic  centimeter.  This 
test  would  be,  therefore,  by  far  too  severe  when  applied  to  a  number 
of  pharmaceutical  preparations,  for  which  reason  the  Pharmacopoeia 
directs  in  many  cases  the  less  sensitive  tests  of  Bettendorff  or  Fleit- 
mann. 

Quantitative  tests  for  the  limit  of  impurities.  While,  as  above 
stated,  even  the  qualitative  tests  are  often  so  made  as  to  be  to  some 
extent  of  a  quantitative  character,  the  U.  S.  P.  recommends  in  many 
cases  methods  by  which  a  stated  limit  of  an  impurity  can  be  detected 
without  the  necessity  of  determining  by  quantitative  analysis  the 
actual  amount  of  the  impurity  present. 

Formerly  it  was,  and  to  some  extent  it  is  now,  customary  to  limit 
the  amount  of  a  permissible  quantity  of  an  impurity  by  referring  to 
the  intensity  of  the  reaction.  In  case  the  impurity  was  to  be  detected 
by  precipitation  (as,  for  instance,  sulphates  or  chlorides  in  potassium 
nitrate)  it  was  stated  that  the  respective  reagents  used  for  the  detec- 
tion (in  the  case  named,  barium  chloride  or  silver  nitrate)  should  not 
produce  more  than  a  very  slight  precipitate,  or  turbidity,  or  cloudi- 
ness, etc.  These  descriptions  are,  of  course,  very  indefinite,  and  the 
conclusion  arrived  at  depends  largely  upon  the  individuality  of  the 
observer. 

In  order  to  obviate  this  uncertainty  the  U.  S.  P.  has  introduced  a 
number  of  more  exact  methods.  These  depend  upon  the  addition  of 


DETECTION  OF  IMPURITIES.  275 

a  definite  quantity  of  a  reagent  capable  of  eliminating  a  certain  quan- 
tity of  the  impurity  from  a  given  quantity  of  the  substance  to  be 
examined.  In  thus  examining  a  preparation  the  impurity  may  or 
may  not  be  present ;  if  present,  the  permissible  quantity  will  be  re- 
moved by  the  operation,  and  if  originally  not  present  in  larger  quan- 
tity, the  substance  will  now  be  found  free  from  the  impurity,  while 
if  present  in  larger  proportions  than  can  be  removed  by  the  quantity 
of  reagent  added,  the  excess  can  be  detected  by  appropriate  tests. 

If  an  excess  of  impurity  is  thus  discovered,  regardless  of  the  fact 
whether  the  excess  be  large  or  small,  the  substance  examined  does 
not  come  up  to  the  pharmacopoeial  requirements. 

For  instance,  the  Pharmacopoeia  fixes  the  limit  of  potassium  chloride 
in  potassium  carbonate  at  0.15  per  cent.,  and  in  order  to  determine 
whether  this  limit  is  exceeded  or  not  the  Pharmacopoeia  directs  the 
addition  of  0.1  c.c.  of  deci-normal  silver  nitrate  solution  to  a  solution 
of  05  gramme  of  potassium  carbonate  in  6  c.c.  of  diluted  nitric  acid 
and  4  c.c.  of  water.  After  removing  the  precipitated  silver  chloride 
by  filtration  no  precipitate  should  be  produced  in  the  filtrate  by  the 
further  addition  of  silver  nitrate  solution.  The  limit  of  many  im- 
purities, which  can  be  separated  by  precipitation  in  definite  quantity, 
is  thus  determined. 

In  other  cases  the  limited  quantity  of  an  impurity  may  be  deter- 
mined without  the  formation  of  a  precipitate,  as,  for  instance,  an 
alkaline  impurity  in  an  otherwise  neutral  salt  by  the  addition  of  a 
standard  acid. 

Thus,  in  potassium  bromide,  the  pharmacopoeial  limit  of  potassium 
carbonate  is  1.38  per  cent.  In  order  to  determine  whether  or  not 
this  limit  is  exceeded,  the  Pharmacopoeia  directs  the  addition  of  0.2 
c.c.  of  normal  sulphuric  acid  to  a  solution  of  1  gramme  of  the  salt 
in  100  c.c.  of  water.  Since  0.1  c.c.  of  normal  sulphuric  acid  is  capa- 
ble of  neutralizing  0.0069  gramme  of  potassium  carbonate,  the  whole 
quantity  allowed,  1.38  per  cent,  or  0.0138  gramme,  would  be  neu- 
tralized by  the  addition  of  the  prescribed  quantity  of  acid,  and  no 
red  tint  should  be  imparted  to  the  liquid  by  adding  a  few  drops  of 
phenol-phtalein  solution  ;  a  red  color  would  indicate  that  more  alkali 
carbonate  was  present  in  the  weighed  sample  than  could  be  neutralized 
by  the  quantity  of  acid  added. 

By  methods  similar  to  those  described,  the  limit  of  many  other 
impurities  is  determined,  as,  for  instance,  the  limit  of  sulphuric  acid 
by  removing  it  with  barium  chloride,  or  that  of  carbonates  in  caustic 
alkalies  by  lime-water. 


276  ANALYTICAL  CHEMISTRY. 

Quantitative  determination  of  the  principal  constituent. 
These  determinations  are  made  in  the  majority  of  cases  volumetric- 
ally,  and  require  no  special  explanation  here,  as  the  methods  have 
been  fully  considered  in  the  previous  chapter.  Gravimetric  methods 
are  used  in  the  determination  of  the  alkaloids  of  cinchona  and  opium, 
and  also  in  a  few  other  cases. 

QUESTIONS. — 364.  What  are  the  sources  of  the  impurities  found  in  chemical 
preparations  ?  365.  Why  is  it  not  obligatory  to  use  chemically  pure  chemicals 
for  medicinal  purposes?  366.  Which  are  the  leading  features  adopted  by  the 
U.  S.  P.  in  the  identification  of  chemical  preparations?  367.  State  the  reasons 
why  the  U.  S.  P.  describes  the  tests  for  impurities  so  minutely.  368.  Why  can 
we  not  use  indiscriminately  either  one  of  a  number  of  reagents  or  tests  by  which 
the  presence  of  the  same  impurity  may  be  indicated  ?  369.  What  is  the  prin- 
ciple applied  in  the  methods  of  the  Pharmacopoeia  for  the  determination  of  a 
permitted  quantity  of  an  impurity?  370.  How  can  we  decide  the  question 
whether  a  sample  of  potassium  acetate  contains  more  than  1  per  cent,  of  potas- 
sium chloride  without  making  a  quantitative  estimation  of  chlorine  ? 


VI. 

CONSIDERATION  OF  CARBON  COMPOUNDS, 
OR  ORGANIC  CHEMISTRY. 


38.  INTRODUCTORY  REMARKS.    ELEMENTARY  ANALYSIS. 

Definition  of  organic  chemistry.  The  term  organic  chemistry 
was  originally  applied  to  the  consideration  of  compounds  formed  in 
plants  and  in  the  bodies  of  animals,  and  these  compounds  were 
believed  to  be  created  by  a  mysterious  power,  called  "  vital  force/' 
supposed  to  reside  in  the  living  organism. 

This  assumption  was  partly  justified  by  the  failure  of  the  earlier 
attempts  to  produce  these  compounds  by  artificial  means,  and  also  by 
the  fact  that  the  peculiar  character  of  the  compounds,  and  the 
numerous  changes  which  they  constantly  undergo  in  nature,  could 
not  be  sufficiently  explained  by  the  experimental  methods .  then 
known,  and  the  laws  then  established. 

It  was  in  accordance  with  these  views  that  a  strict  distinction  was 
made  between  inorganic  and  organic  compounds,  and  accordingly 
between  inorganic  and  organic  chemistry,  the  latter  branch  of  the 
science  considering  the  substances  formed  in  the  living  organism 
and  those  compounds  which  were  produced  by  their  decomposition. 

Since  that  time  it  has  been  shown  that  many  substances  which 
formerly  were  believed  to  be  exclusively  produced  in  the  living 
organism,  under  the  influence  of  the  so-called  vital  force,  can  be 
formed  artificially  from  inorganic  matter,  or  by  direct  combination 
of  the  elements.  It  was  in  consequence  of  this  fact  that  the  theory 
of  the  supposed  "  vital  force,"  by  which  organic  substances  could  be 
formed  exclusively,  had  to  be  abandoned. 

An  organic  compound,  according  to  modern  views,  is  simply  a 
compound  of  carbon  generally  containing  hydrogen,  frequently  also 
oxygen  and  nitrogen,  and  sometimes  other  elements. 

Organic  chemistry  may  consequently  be  defined  as  the  chemistry  of 
\  carbon  compounds.     The  old  familiar  terms,  organic  compounds  and 
organic  chemistry,  are,  however,  still  in  general  use. 

(277) 


278  CONSIDERATION  OF  CARSON  COMPOUNDS. 

In  a  strictly  systematically  arranged  text-book  of  chemistry  organic 
compounds  should  be  considered  in  connection  with  the  element 
carbon  itself,  but  as  these  carbon  compounds  are  so  numerous,  their 
composition  often  so  complicated,  and  the  decompositions  which  they 
suffer  under  the  influence  of  heat  or  other  agents  so  varied,  it  has 
been  found  best  for  purposes  of  instruction  to  defer  the  consideration 
of  these  compounds  until  the  other  elements  and  their  combinations 
have  been  studied. 

Elements  entering-  into  organic  compounds.  Organic  com- 
pounds contain  generally  but  a  small  number  of  elements.  These 
are,  besides  carbon,  chiefly  hydrogen,  oxygen,  and  nitrogen,  and 
sometimes  sulphur  and  phosphorus.  Other  elements,  however,  enter 
occasionally  into  organic  compounds,  and  by  artificial  means  all 
metallic  and  non-metallic  elements  may  be  made  to  enter  into  organic 
combinations. 

Here  the  question  presents  itself :  Why  is  it  that  the  four  elements 
carbon,  hydrogen,  oxygen,  and  nitrogen  are  capable  of  producing 
such  an  immense  number  (in  fact,  millions)  of  different  combinations? 
To  this  question  but  one  answer  can  be  given,  which  is  that  these 
four  elements  differ  more  widely  from  each  other,  in  their  chemical 
and  physical  properties,  than  perhaps  any  other  four  elements. 

Carbon  is  a  black,  solid  substance,  which  has  never  yet  been  fused 
or  volatilized,  while  hydrogen,  oxygen,  and  nitrogen  are  colorless 
gases  which  can  only  be  converted  into  liquids  with  difficulty.  More- 
over, hydrogen  is  very  combustible,  oxygen  is  a  supporter  of  combus- 
tion, whilst  nitrogen  is  perfectly  indifferent.  Finally,  hydrogen  is 
univalent,  oxygen  bivalent,  nitrogen  trivalent,  and  carbon  quadri- 
valent. These  elements  are,  therefore,  capable  of  forming  a  greater 
number  and  a  greater  variety  of  compounds  than  would  be  the 
case  if  they  were  elements  of  equal  valence  and  of  similar  proper- 
ties. 

It  will  be  shown  later  that  carbon  atoms  have,  to  a  higher  degree 
than  the  atoms  of  any  other  element,  the  power  of  combining  with 
one  another  by  means  of  a  portion  of  the  affinities  possessed  by  each 
atom,  thus  increasing  the  possibilities  of  the  formation  of  complex 
compounds. 

General  properties  of  organic  compounds.  The  substances 
formed  by  the  union  of  the  four  elements  just  mentioned  have  prop- 
erties in  some  respects  intermediate  to  those  of  their  components. 


INTRODUCTORY  REMARKS.  279 

Thus,  no  organic  substance  is  either  permanently  solid l  like  carbon, 
nor  an  almost  permanent  gas  like  hydrogen,  oxygen,  and  nitrogen. 

Some  organic  substances  are  solids,  others  liquids,  others  gases  ; 
they  are  generally  solids  when  the  carbon  atoms  predominate ;  they 
are  liquids  or  gases  when  the  gaseous  elements,  and  especially  hydro- 
gen, predominate ;  likewise,  it  may  also  be  said  that  compounds  con- 
taining a  small  number  of  atoms  in  the  molecule  are  gases  or  liquids 
which  are  easily  volatilized ;  they  are  liquids  of  high  boiling- 
points,  or  solids,  when  the  number  of  atoms  forming  the  molecules 
is  large. 

The  combustible  property  of  carbon  and  hydrogen  is  transferred 
to  all  organic  substances,  every  one  of  which  will  burn  when  suffi- 
ciently heated  in  atmospheric  air.  (If  carbon  dioxide,  carbonic  acid 
and  its  salts  be  considered  organic  compounds,  we  have  an  exception 
to  the  rule,  as  they  are  not  combustible.) 

The  properties  possessed  by  organic  compounds  are  many  and 
widely  different.  There  are  organic  acids,  organic  bases,  and  organic 
neutral  substances;  there  are  some  organic  compounds  which  are 
perfectly  colorless,  tasteless,  and  odorless,  whilst  others  show  every 
possible  variety  of  color,  taste,  and  odor ;  many  serve  as  food,  whilst 
others  are  most  poisonous ;  in  short,  organic  substances  show  a  greater 
variety  of  properties  than  the  combinations  formed  by  any  other 
four  elements. 

And  yet,  the  cause  of  all  the  boundless  variety  of  organic  matter 
is  that  peculiar  attraction  called  chemical  affinity,  acting  between  the 
atoms  of  a  comparatively  small  number  of  elements  and  uniting  them 
in  many  thousand  different  proportions. 

It  would,  of  course,  be  entirely  inconsistent  with  the  object  of  this 
book,  if  all  the  thousands  of  organic  substances  already  known  (the 
number  of  which  is  continually  being  increased  by  new  discoveries) 
were  to  be  considered,  or  even  mentioned.  It  must  be  sufficient  to 
state  the  general  properties  of  the  various  groups  of  organic  sub- 
stances, to  show  by  what  processes  they  are  produced  artificially  or 
how  they  are  found  in  nature,  how  they  may  be  recognized  and 
separated,  and,  finally,  to  point  out  those  members  of  each  group 
which  claim  a  special  attention  for  one  reason  or  another. 

Difference  in  the  analysis  of  organic  and  inorganic  sub- 
stances. The  analysis  of  organic  substances  differs  from  that  of 

1    Non-volatile  organic  substances  are  decomposed  by  heat  with   generation  of  volatile 
products. 


280  CONSIDERATION  OF  CARBON  COMPOUNDS. 

inorganic  substances,  in  so  far  as  the  qualitative  examination  of  an 
organic  substance  furnishes  in  many  cases  but  little  proof  of  the  true 
nature  of  the  substance  (except  that  it  is  organic),  whilst  the  quali- 
tative analysis  of  an  inorganic  substance  discloses  in  most  cases  the 
true  nature  of  the  substance  at  once. 

For  instance :  If  a  white,  solid  substance,  upon  examination,  be 
found  to  contain  potassium  and  iodine,  and  nothing  else,  the  conclu- 
sion may  at  once  be  drawn  that  the  compound  is  potassium  iodide, 
containing  39  parts  by  weight  of  potassium,  and  126.5  parts  by 
weight  of  iodine.  Or,  if  another  substance  be  examined,  and  found 
to  be  composed  of  mercury  and  chlorine,  the  conclusion  may  be  drawn 
that  the  compound  is  either  mercurous  or  mercuric  chloride,  as  no 
other  compounds  containing  these  two  elements  are  known,  and 
whether  the  examined  substance  be  the  lower  or  higher  chloride  of 
mercury,  or  a  mixture  of  both,  can  easily  be  determined  by  a  few 
simple  tests. 

Whilst  thus  the  qualitative  examination  discloses  the  nature  of  the 
substance,  it  is  different  with  organic  compounds.  Many  thousand 
times  the  analysis  might  show  carbon,  hydrogen,  and  oxygen  to  be 
present,  and  yet  every  one  of  the  compounds  examined  might  be 
entirely  different ;  it  is  consequently  not  only  the  quality  of  the  ele- 
ments, but  chiefly  the  quantity  present  which  determines  the  nature 
of  an  organic  substance,  and  in  order  to  identify  an  organic  substance 
with  certainty,  it  frequently  becomes  necessary  to  make  a  quantitative 
determination  of  the  various  elements  present,  and  this  quantitative 
analysis  by  which  the  elements  in  organic  substances  are  determined 
is  generally  called  ultimate  or  elementary  analysis. 

There  are,  however,  for  many  organic  substances  such  character- 
istic tests  that  these  substances  may  be  recognized  by  them  ;  these 
reactions  will  be  mentioned  in  the  proper  places. 

An  analysis  by  which  different  organic  substances,  when  mixed 
together,  are  separated  from  each  other  is  frequently  termed  proximate 
analysis.  Such  an  analysis  includes  the  separation  and  determination 
of  essential  oils,  fats,  alcohols,  sugars,  resins,  organic  acids,  albuminous 
substances,  etc.,  and  is  one  of  the  most  difficult  branches  of  analytical 
chemistry. 

Qualitative  analysis  of  organic  substances.  The  presence  of 
carbon  in  a  combustible  form  is  decisive  in  regard  to  the  organic 
nature  of  a  compound.  If,  consequently,  a  substance  burns  with 
generation  of  carbon  dioxide  (which  maybe  identified  bypassing  the 


ELEMENTARY  ANALYSIS. 


281 


gas  through  lime-water),  the  organic  nature  of  this  substance  is 
established. 

The  presence  of  hydrogen  can  be  proven  by  allowing  the  gaseous 
products  of  the  combustion  to  pass  through  a  cool  glass  tube,  when 
drops  of  water  will  be  deposited. 

It  is  difficult  to  show  by  qualitative  analysis  the  presence  or 
absence  of  oxygen  in  an  organic  compound,  and  its  determination  is 
therefore  generally  omitted. 

The  presence  of  nitrogen  is  determined  by  heating  the  substance 
with  dry  soda-lime  (a  mixture  of  two  parts  of  calcium  hydroxide  and 
one  part  of  sodium  hydroxide),  when  the  nitrogen  is  converted  into 
ammonia  gas,  which  may  be  recognized  by  its  odor  or  by  its  action 
on  paper  moistened  with  solution  of  cupric  sulphate,  a  dark-blue 
color  indicating  ammonia. 

Ultimate  or  elementary  analysis.  While  the  student  must  be 
referred  to  books  on  analytical  chemistry  for  a  detailed  description  of 
the  apparatus  required  and  the  methods  employed  for  elementary 
analysis,  it  may  here  be  stated  that  the  quantitative  determination  of 
carbon  and  hydrogen  is  generally  accomplished  by  the  following  pro- 
A weighed  quantity  of  the  pure  and  dry  substance  is  mixed 


cess 


FIG.  38. 


Gas-furnace  for  organic  analysis. 

with  a  large  excess  of  dry  cupric  oxide,  and  this  mixture  is  introduced 
into  a  glass  tube,  the  open  end  of  which  is  connected  by  means  of  a 
perforated  cork  and  tubing  with  two  glass  vessels,  the  first  one  of 
which  (generally  a  U-shaped  tube)  is  filled  with  pieces  of  calcium 
chloride,  the  other  (usually  a  tube  provided  with  several  bulbs)  with 
solution  of  potassium  hydroxide.  The  two  glass  vessels,  containing 
the  substances  named,  are  weighed  separately  after  having  been 


I 


282  CONSIDERATION  OF  CARBON  COMPOUNDS. 

filled.  Upon  heating  the  combustion-tube  in  a  suitable  furnace,  the 
organic  matter  is  burned  by  the  oxygen  of  the  cupric  oxide,  the. 
hydrogen  is  converted  into  water  (steam),  which  is  absorbed  by  the 
calcium  chloride,  and  the  carbon  is  converted  into  carbon  dioxide, 
which  is  absorbed  by  the  potassium  hydroxide.  The  apparatus  repre- 
sented in  Fig.  38  shows  the  gas-furnace  in  which  rests  the  combustion- 
tube  with  calcium  chloride  tube  and  potash  bulb  attached.  Upon 
re-weighing  the  two  absorbing  vessels  at  the  end  of  the  operation,  the 
increase  in  weight  will  indicate  the  quantity  of  water  and  carbon 
dioxide  formed  during  the  combustion,  and  from  these  figures  the 
amount  of  carbon  and  hydrogen  present  in  the  organic  matter  may 
easily  be  calculated. 

For  instance  :  0.81  gramme  of  a  substance  having  been  analyzed, 
furnishes,  of  carbon  dioxide  1.32  gramme,  and  of  water  0.45  gramme. 
As  every  44  parts  by  weight  of  carbon  dioxide  contain  12  parts  by 
weight  of  carbon,  the  above  1.32  gramme  contains  of  carbon  0.36 
gramme,  or  44.444  per  cent.  As  every  18  parts  of  water  contain  2 
parts  of  hydrogen,  the  above  0.45  gramme  consequently  contains  0.05 
gramme,  or  6.172  per  cent. 

Oxygen  is  scarcely  ever  determined  directly,  but  generally  indi- 
rectly, by  determining  the  quantity  of  all  other  elements  and  deduct- 
ing their  weight,  calculated  to  percentages  from  100.  The  difference 
is  oxygen. 

If,  in  the  above  instance,  44.444  per  cent,  of  carbon  and  6.172  per 
cent,  of  hydrogen  were  found  to  be  present,  and  all  other  elements, 
except  oxygen,  to  be  absent,  the  quantity  of  oxygen  is,  then,  equal 
to  49.384  per  cent,  and  the  composition  of  the  substance  is  as  follows : 

Carbon        .         .        .        .  .         .        .     44.444  per  cent. 

Hydrogen 6.172         " 

Oxygen 49.384        " 

100  000 

Determination  of  nitrogen.  Nitrogen  is  generally  determined 
by  heating  the  substance  with  soda-lime  and  passing  the  generated 
ammonia  gas  through  hydrochloric  acid  contained  in  a  suitable  glass 
vessel.  Upon  evaporation  of  the  acid  solution  in  a  weighed  platinum 
dish  over  a  water-bath,  ammonium  chloride  is  left,  from  the  weight 
of  which  compound  the  quantity  of  nitrogen  may  be  calculated.  Or 
the  ammonia  gas  may  be  passed  through  a  measured  volume  of 
normal  hydrochloric  acid  and  the  unsaturated  portion  of  the  acid 
determined  volumetrically. 


ELEMENTAR  Y  ANAL  YSIS.  283 

Determination  of  sulphur  and  phosphorus.  These  elements  are 
determined  by  mixing  the  organic  substance  with  sodium  carbonate 
and  nitrate,  and  heating  the  mixture  in  a  crucible.  The  oxidizing 
action  of  the  nitrate  converts  all  carbon  into  carbon  dioxide,  hydrogen 
into  water,  sulphur  into  sulphuric  acid,  phosphorus  into  phosphoric 
acid.  The  latter  two  acids  combine  with  the  sodium  of  the  sodium 
carbonate,  forming  sulphate  and  phosphate  of  sodium.  The  fused 
mass  is  dissolved  in  water,  and  sulphuric  acid  precipitated  by  barium 
chloride,  phosphoric  acid  by  magnesium  sulphate  and  ammonium 
hydroxide  and  chloride.  From  the  weight  of  barium  sulphate  and 
magnesium  pyrophosphate  the  weight  of  sulphur  and  phosphorus  is 
calculated. 

Determination  of  atomic  composition  from  results  obtained 
by  elementary  analysis.  The  elementary  analysis  gives  the  quan- 
tity of  the  various  elements  present  in  percentages,  and  from  these 
figures  the  relative  number  of  atoms  may  be  found  by  dividing  the 
figures  by  the  respective  atomic  weights.  For  instance  :  The  analysis 
above  mentioned  gave  the  composition  of  a  compound,  as  carbon 
44.444  per  cent.,  hydrogen  6.172  per  cent.,  and  oxygen  49.384  per 
cent.  By  dividing  each  quantity  by  the  atomic  weight  of  the  respec- 
tive element,  the  following  results  are  obtained  : 

44.444 


12 
6.172 

I 

49.384 
16 


==  3.703 
=  6.172 
=  3.087 


The  figures  3.703,  6.172,  and  3.087,  represent  the  relative  number 
of  atoms  present  in  a  molecule  of  the  compound  examined.  In  order 
to  obtain  the  most  simple  proportion  expressing  this  relation,  the 
greatest  divisor  common  to  the  whole  has  to  be  found,  a  task  which 
is  sometimes  rather  difficult  on  account  of  slight  errors  made  in  the 
quantitative  determination  itself.  In  the  above  case,  0.6172  is  the 
greatest  divisor,  which  gives  the  following  results  : 
3.703  _  .  6.172  _  .  3.087  ' 


0.6172  '    0.6172  '    0.6172 


, 


The  simplest  numbers  of  atoms  are,  accordingly,  carbon  6,  hydrogen 
10,  oxygen  5,  or  the  composition  is  C6H10O5. 

Empirical  and   molecular  formulas.     A  chemical  formula  is 
termed  empirical  when  it  merely  gives  the  simplest  possible  expression 


284  CONSIDERATION  OF  CARBON  COMPOUNDS. 

of  the  composition  of  a  substance.  In  the  above  case,  the  formula 
C6H10O5  would  be  the  empirical  formula.  It  might,  however,  be 
possible  that  this  formula  did  not  represent  the  actual  number  of 
atoms  in  the  molecule,  which  might  contain,  for  instance,  twice  or 
three  times  the  number  of  atoms  given,  in  which  case  the  true  com- 
position would  be  expressed  by  the  formula  C12H20O10  or  C18H30O15. 

If  it  could  be  proven  that  one  of  the  latter  formulas  is  the  correct 
one,  it  would  be  termed  the  molecular  formula,  because  it  expresses 
not  only  the  numerical  relations  existing  between  the  atoms,  but  also 
the  absolute  number  of  atoms  of  each  element  contained  in  the 
molecule. 

The  best  method  for  determining  the  actual  number  of  atoms  con- 
tained in  the  molecule  is  the  determination  of  the  specific  weight  of 
the  gaseous  compound,  taking  hydrogen  as  the  unit.  For  instance  : 
Assume  the  analysis  of  a  liquid  substance  gave  the  following  result : 

Carbon -     .     92.308  per  cent. 

Hydrogen .        .       7-692 

100.000 

From  this  result  the  empirical  formula,  CH,  is  deducted  by  apply- 
ing the  method  stated  above.  If  this  formula  were  the  molecular 
formula,  the  density  of  the  vapors  of  the  substance  would,  when  com- 
pared with  hydrogen  (according  to  the  law  of  Avogadro),  be  equal  to 
6.5,  because  a  molecule  of  hydrogen  weighs  2  and  a  molecule  of  the 
compound  CH  weighs  13. 

Suppose,  however,  the  density  of  the  gaseous  substance  is  found  to 
be  39,  then  the  molecular  formula  would  be  expressed  by  C6H6, 
because  its  molecular  weight  (6  X  12  +  6  X  l)is  equal  to  78,  which 
weight,  when  compared  with  the  molecular  weight  of  hydrogen  =  2,, 
gives  the  proportions  78  :  2,  or  39  :  1. 

Not  all  organic  compounds  can  be  converted  into  gases  or  vapors 
without  undergoing  decomposition,  and  the  determination  of  the 
molecular  formulas  of  such  compounds  has  to  be  accomplished  by 
other  methods.  If  the  substance,  for  instance,  is  an  acid  or  a  base,, 
the  molecular  formula  may  be  determined  by  the  analysis  of  a  salt 
formed  by  these  substances.  For  instance  :  The  empirical  formula  of 
acetic  acid  is  CH2O ;  the  analysis  of  the  potassium  acetate,  however, 
shows  the  composition  KC2H3O2,  from  which  the  molecular  formula 
HC2H3O2  is  deducted  for  acetic  acid. 

In  many  cases,  however,  it  is  as  yet  absolutely  impossible  to  give 
with  certainty  the  molecular  formula  of  some  compounds. 


ELEMENTAR  Y  ANAL  YSIS.  285 

Rational,  constitutional,  structural,  or  graphic  formulas. 
These  formulas  are  intended  to  represent  the  theories  which  have 
been  formed  in  regard  to  the  arrangement  of  the  atoms  within  the 
molecule,  or  to  represent  the  modes  of  the  formation  and  decom- 
position of  a  compound,  or  the  relation  which  allied  compounds  bear 
to  one  another. 

The  molecular  formula  of  acetic  acid,  for  instance,  is  C2H4O2,  but 
different  constitutional  formulas  have  been  used  to  represent  the 
structure  of  the  acetic  acid  molecule. 

Thus,  H.C2H3O2  is  a  formula  analogous  to  H.NO3,  indicating  that 
acetic  acid  (analogous  to  nitric  acid),  is  a  monobasic  acid,  containing 
one  atom  of  hydrogen,  which  can  be  replaced  by  metallic  atoms. 

CaHgO.OH1  is  a  formula  indicating  that  acetic  acid  is  composed  of 
two  univaleut  radicals  which  may  be  taken  out  of  the  molecule  and 
replaced  by  other  atoms  or  groups  of  atoms.  This  formula  indicates 
also  that  acetic  acid  is  analogous  to  hydroxides,  the  radical  C2H3O 
having  replaced  one  atom  of  hydrogen  in  H2O. 

CH3.CO2Hl  is  a  formula  indicating  that  acetic  acid  is  composed  of 
the  two  compound  radicals,  methyl  and  carboxyl. 

It  may  be  said  finally,  that  quite  a  number  of  other  rational 
formulas  have  been  applied,  or,  at  least,  have  been  proposed  by 
different  chemists  and  at  different  times,  to  represent  the  structure  of 
acetic  acid,  but  it  should  be  remembered  that  these  formulas  are  not 
intended  to  represent  the  actual  arrangement  of  the  atoms  in  space, 
but  only,  as  it  were,  their  relative  mode  of  combination,  showing 
which  atoms  are  combined  directly  and  which  only  indirectly,  that 
is,  through  the  medium  of  others. 

QUESTIONS. — 371.  What  is  organic  chemistry,  according  to  modern  views? 
372.  Mention  the  chief  four  elements  entering  into  organic  compounds,  and 
name  the  elements  which  may  be  made  to  enter  into  organic  compounds  by 
artificial  processes.  373.  State  the  reason  why  the  four  elements,  carbon, 
hydrogen,  oxygen,  and  nitrogen,  are  better  adapted  to  form  a  large  number  of 
compounds  than  most  other  elements.  374.  State  the  general  properties  of 
organic  compounds.  375.  Why  does  a  qualitative  analysis  of  an  organic  com- 
pound, in  most  cases,  not  disclose  its  true  nature  ?  376.  By  what  test  may  the 
organic  nature  of  a  compound  be  established  ?  377.  By  what  tests  may  the 
presence  of  carbon,  hydrogen,  and  nitrogen  be  demonstrated  in  organic  com- 
pounds? 378.  State  the  methods  by  which  the  elements  carbon,  hydrogen, 
oxygen,  sulphur,  and  phosphorus  are  determined  quantitatively.  379.  By 
what  general  method  may  a  formula  be  deducted  from  the  results  of  a  quanti- 
tative analysis  ?  380.  What  is  meant  by  an  empirical,  molecular,  and  consti- 
tutional formula;  how  are  they  determined;  and  what  is  the  difference  between 
them  ? 


286  CONSIDERATION  OF  CARBON  COMPOUNDS. 


39.    CONSTITUTION,  DECOMPOSITION,   AND  CLASSIFICATION 
OF  ORGANIC  COMPOUNDS. 

Radicals  or  residues.  The  nature  of  a  radical  or  residue  has 
been  stated  already  in  Chapter  8,  but  the  important  part  played  by 
radicals  in  organic  compounds  renders  it  necessary  to  consider  them 
more  fully. 

A  radical  is  an  unsaturated  group  of  atoms  obtained  by  removal 
of  one  or  more  atoms  from  a  saturated  compound.  It  is  not  neces- 
sary that  this  removal  of  atoms  should  be  practically  accomplished  in 
order  to  call  a  group  of  atoms  a  radical,  but  it  is  sufficient  to  prove 
that  the  unsaturated  group  of  atoms  exists  as  such  in  a  number  of 
compounds,  and  that  it  can  be  transferred  from  one  compound  into 
another  without  suffering  decomposition. 

Kadicals  exist  in  organic  and  inorganic  compounds ;  an  inorganic 
radical  spoken  of  heretofore  is  the  water  residue  or  hydroxyl,  OH, 
obtained  by  removal  of  one  atom  of  hydrogen  from  one  molecule  of 
water.  Hydroxyl  does  not  exist  in  the  separate  state,  but  it  exists  in 
hydrogen  dioxide,  H2O2,  or  HO — OH,  and  is  also  a  constituent  of  the 
various  hydroxides,  as,  for  instance,  of  KOH,  Ca(OH)2,  Fe2(OH)6,  etc. 

If  one  atom  of  hydrogen  be  removed  from  the  saturated  hydro- 
carbon methane,  CH4,  the  univalent  residue  methyl,  CH3,  is  left, 
which  is  capable  of  combining  with  univalent  elements,  as  in  methyl 
chloride,  CH3C1,  or,  with  univalent  residues,  as  in  methyl  hydroxide, 
CH3OH. 

If  two  atoms  of  hydrogen  be  removed  from  CH4,  the  bivalent  resi- 
due methylene,  CH2,  is  left,  capable  of  forming  the  compounds 
CH2C12,  CH2(OH)2,  etc. 

If  three  atoms  of  hydrogen  be  removed  from  CH4,  the  trivalent 
residue  CH  is  left,  capable  of  combining  with  three  atoms  of  univa- 
lent elements,  as  in  CHC13,  or  with  another  trivalent  radical,  etc. 

Chains.  The  expression,  chain,  designates  a  series  of  multivalent 
atoms  (generally,  but  not  necessarily,  of  the  same  element),  held 
together  in  such  a  manner  that  affinities  are  left  unsaturated.  For 

instance : 

— O— O—     —0-0-0—     —  O— 0-O-0-, 

are  oxygen  chains,  each  one  of  which  has  two  free  affinities  which 
may  be  saturated,  for  instance,  with  the  following  results  : 

H— O— O— H,        H— O— O— 0-C1,        H-O— 0—0-0— Cl, 

Hydrogen  peroxide.  Chloric  acid.  Perchloric  acid. 


CONSTITUTION  OF  ORGANIC  COMPOUNDS.  287 

In  a  similar  manner,  carbon  atoms  unite,  forming  chains,  as,  for 
instance  : 

II  III  I      I      I     I 

_  C—  C—  ,        —  C—  C—  C—  ,        —  C—  C—  C—  C—  ,  etc. 

II  III  till 

The  above  carbon  chains  have  6,  8,  and  10  free  affinities,  respect- 
ively, which  may  be  saturated  by  the  greatest  variety  of  atoms  or 
radicals.  The  chain  combination  of  carbon,  above  indicated  by  the 
first  three  members  of  a  series,  may,  as  far  as  is  known,  be  continued 
indefinitely.  This  fact,  in  connection  with  the  possibility  of  saturat- 
ing the  free  affinities  with  various  atoms  or  radicals,  indicates  the 
almost  unlimited  number  of  possible  combinations  to  be  formed  in 
this  way.  In  fact,  the  existence  of  such  an  enormous  number  of 
carbon  compounds  is  greatly  due  to  the  property  of  carbon  to  form 
these  chains. 

It  is  not  always  the  case  that  the  atoms  when  forming  a  chain  are 
united  by  one  affinity  only,  as  above,  but  they  may  be  united  by  two 
or  three  affinities,  as  indicated  by  the  compounds  C2H4  and  C2H2,  the 
graphic  formulas  of  which  may  be  represented  by 

H 


Finally,  it  is  assumed  that  the  carbon  atoms  are  united  partially 
by  double  and  partially  by  single  union,  as,  for  instance,  in  the  so- 
called  closed  chain  of  C6,  capable  of  forming  the  saturated  hydrocarbon 
benzene,  C6H6  : 


H 


& 

\  H/  So/    \H 

1  A 

A  chain  has  also  been  termed  a  skeleton,  because  it  is  that  part  of  an  organic 
compound  around  which  the  other  elements  or  radicals  arrange  themselves, 
filling  up,  as  it  were,  the  unsaturated  affinities. 

Homologous  series.  This  term  is  applied  to  any  series  of  organic 
compounds  the  terms  or  members  of  which,  preceding  or  following 
each  other,  differ  by  CH2.  Moreover,  the  general  character,  the  con- 
stitution, and  the  general  properties  of  the  members  of  an  homologous 
series  are  similar. 

The  explanation  regarding  the  formation  of  an  homologous  series 
is  to  be  found  in  the  above-described  property  of  carbon  to  form 


288  CONSIDERATION  OF  CARBON  COMPOUNDS. 

chains.  By  saturating,  for  instance,  the  affinities  in  the  open  carbon 
chains  mentioned  above,  we  obtain  the  compounds  CH4,  C2H6,  C3H8, 
C4H10,  etc. 

H  HH  HHH  HHHH 

H— C— H,    H— C-C— H,    H— C— C— C— H,    H— C— C— C— C— H,  etc. 

H  HH  HHH  HHHH 


Many  homologous  series  of  various  organic  compounds  are  known, 
as,  for  instance  : 

C  H3  Cl,  C  H4  O,  C  H2  O2. 

C2H5C1,  C2H60,  C2H402. 

C3H7C1,  C3H80,  C3H602. 

C4H9C1,  C4H100,  C4H802. 

C5HnCl,  C5H120,  C5H1002. 

etc.                                   etc.  etc. 

Types.  It  has  been  proposed  to  select  some  substances  in  which  the  arrange- 
ment of  atoms  in  the  molecules  may  betaken  as  representative  of  whole  classes 
of  other  substances,  the  molecules  of  which  have  a  similar  arrangement,  and 
these  normal  substances  have  been  termed  types.  Most  substances  may  be 
classified  under  the  following  five  types  : 


I. 

II. 

III. 

IV. 

V. 

Hydrogen. 

Water. 

Ammonia. 

Methane. 

Phosphoric  chloride. 

H 

Cl 

H-H, 

H—  0—  H, 

N^H, 

c<E 

1  /ci 

"> 

1      H 

|  XC1 

H 

Cl 

By  replacing  the  constituents  of  these  types  by  other  elements  or  radicals  of 
equal  valence,  most  of  the  compounds  known  (both  organic  and  inorganic)  may 
be  classed  in  one  of  these  types. 

The  following  five  substances  may,  for  instance,  be  said  to  have  an  atomic 
arrangement  similar  to  the  types  above  stated : 

I.  II.  III.  IV.  V. 

Hydrochloric       Potassium  Arsenous  Ethane.  Phosphoric 

acid.  hydroxide.  chloride.  oxychloride. 


CH3  O 

/Cl 

H—  Cl,        K—  O—  H,          As^-Cl, 

^Cl 

H  Cl 


3 

|      H  ||      Cl 

Of  P( 

|  XH  |  XC1 


The  graphic  representation  of  the  constitution  of  compounds  according  to 
types  has  greatly  aided  in  disclosing  their  structure,  and  is  frequently  used  to 
give  a  picture,  as  it  were,  of  the  theoretical  views  held  regarding  the  atomic 
arrangement. 

Substitution  is  a  term  used  for  those  reactions  or  chemical  changes 
which  depend  on  the  replacement  of  an  atom  or  a  group  of  atoms  by 


CONSTITUTION  OF  ORGANIC  COMPOUNDS.  289 

other  atoms  or  groups  of  atoms.  Substitution  takes  place  in  organic 
or  inorganic  substances,  and  its  nature  may  be  illustrated  by  the  fol- 
lowing instances : 

K    +    H2O    =    KOH    +    H. 
Potassium.      Water.         Potassium     Hydrogen, 
hydroxide. 

C2H402    +     2C1       :    C2H3C102    +     HC1. 

Acetic  acid.      Chlorine.    Monochloracetic   Hydrochloric 
acid.  "    acid. 

C6H6    +    HN03        :    C6H5N02     +     H2O. 
Benzene.       Nitric  acid.      Nitro-benzene.          Water. 

Derivatives.  This  term  is  applied  to  bodies  derived  from  others 
by  some  kind  of  decomposition,  generally  by  substitution.  Thus, 
nitro-benzene  is  a  derivative  of  benzene;  chloroform,  CHC13,  is  a 
derivative  of  methane,  CH4,  obtained  from  the  latter  by  replacement 
of  three  atoms  of  hydrogen  by  the  same  number  of  atoms  of  chlorine. 

Isomerism.  Two  or  more  substances  may  have  the  same  elements 
in  the  same  proportion' by  weight  (or  the  same  centesimal  composi- 
tion), and  yet  be  different  bodies,  showing  different  properties.  Such 
substances  are  called  isomeric  bodies.  Two  kinds  of  isomerism  are 
distinguished,  viz.,  metamerism  and  polymerism. 

Metamerism.  Substances  are  metameric  when  their  molecules  con- 
tain equal  numbers  of  atoms  of  the  same  elements.  Thus,  the  oils 
of  juniper,  turpentine,  lemon,  etc.,  all  have  the  molecular  formula 
C10H16,  and  yet  they  have  different  physical  properties,  and  may  be 
distinguished  by  their  odor,  by  their  action  on  polarized  light,  etc. 

The  explanation  given  regarding  this  difference  of  properties  is, 
that  the  atoms  are  arranged  differently  within  the  molecule.  In 
some  cases  this  arrangement  is  as  yet  unknown,  in  other  cases  struc- 
tural or  graphic  formulas  showing  this  atomic  arrangement  may  be 
given. 

For  instance  :  Acetic  acid  and  methyl  formate  both  have  the  com- 
position C2H4O2,  but  the  arrangement  of  the  atoms  (or  the  structure) 
is  very  different,  as  shown  by  the  formulas  : 

Acetic  acid.  Methyl  formate. 

C2H30\Q  CHO\0 

H/U  CH3/°' 

As  another  instance  may  be  mentioned  the  compound 
which  represents  either  ammonium  cyanate  or  urea  : 

Ammonium  cyanate.  Urea. 

NH2\nn 
NHJ/00' 

19 


290  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Polymerism.  Substances  are  said  to  be  polymeric  when  they  have 
the  same  centesimal  composition,  but  a  different  molecular  weight,  or, 
in  other  words,  when  one  substance  contains  some  multiple  of  the 
number  of  each  of  the  atoms  contained  in  the  molecule  of  the  other. 

For  instance,  some  volatile  oils  have  the  composition  C20H32,  which 
is  double  the  number  of  atoms  contained  in  oil  of  turpentine,  C10H16  ; 
acetylene,  C2H2,  is  polymeric  with  benzene,  C6H6  ;  acetic  acid, 
C2H4O2,  is  polymeric  with  grape-sugar,  C6H12O6,  etc. 

Various  modes  of  decomposition.  The  principal  changes  which 
a  molecule  may  suffer  are  as  follows  : 

a.  The  atoms  may  arrange  themselves  differently  within  the  mole- 
cule.    Ammonium  cyanate,  NH4CNO,  is  easily  converted  into  urea, 
CO(NH2)2. 

b.  A  molecule  may  split  up  into  two  or  more  molecules.     For 

instance  : 

C6H1206    :  :    2C2H60      +      2C02. 
Grape-sugar.          Alcohol.          Carbon  dioxide. 

c.  Two  molecules,  either  of  the  same  kind,  or  of  different  sub- 
stances, may  unite  together  directly  : 


-f     2Br      =      C2H4Br2. 
Ethylene.      Bromine.       Ethylene  bromide. 

d.  Atoms  may  be  removed  from  a  compound  without  replacing 
them  by  other  atoms  : 

C2H6O    +    O    =    C2H4O    +    H2O. 
Alcohol.       Oxygen.      Aldehyde.          Water. 

e.  Atoms  may  be  removed  and   replaced  by  others  at  the  same 
time  (substitution)  : 

C2H4O2    -f    2C1       :    C2H3C102      +      HC1. 

Acetic  acid.      Chlorine.    Monochloracetic      Hydrochloric 
acid.  acid. 

Action  of  heat  upon  organic  substances.  As  a  general  rule, 
organic  bodies  are  distinguished  by  the  facility  with  which  they 
decompose  under  the  influence  of  heat  or  chemical  agents  ;  the  more 
complex  the  body  is,  the  more  easily  does  it  undergo  decomposition 
or  transformation. 

Heat  acts  differently  upon  organic  substances,  some  of  which  may 
be  volatilized  without  decomposition,  whilst  others  are  decomposed 
by  heat  with  generation  of  volatile  products.  This  process  of  heating 
non-volatile  organic  substances  in  such  a  manner  that  the  oxygen  of 
the  atmospheric  air  has  no  excess,  and  to  such  an  extent  that  decom- 
position takes  place,  is  called  dry  or  destructive  distillation. 


DECOMPOSITION  OF  ORGANIC  COMPOUNDS.  291 

The  nature  of  the  products  formed  during  this  process  varies  not 
only  with  the  nature  of  the  substance  heated,  but  also  with  the  tem- 
perature applied  during  the  operation.  The  products  formed  by 
destructive  distillation  are  invariably  less  complex  in  composition, 
that  is,  have  a  smaller  number  of  atoms  in  the  molecule,  than  the 
substance  which  suffered  decomposition  ;  in  other  words,  a  complex 
molecule  is  split  up  into  two  or  more  molecules  less  complex  in 
composition. 

Otherwise,  the  products  formed  show  a  great  variety  of  properties ; 
some  are  gases,  others  volatile  liquids  or  solids,  some  are  neutral, 
others  basic  or  acid  substances.  In  most  cases  of  destructive  distilla- 
tion a  non-volatile  residue  is  left,  which  is  nearly  pure  carbon. 

Action  of  oxygen  upon  organic  substances.  Combustion. 
Decay.  All  organic  substances  are  capable  of  oxidation,  which 
takes  place  either  rapidly  with  the  evolution  of  heat  and  light  and  is 
called  combustion,  or  it  takes  place  slowly  without  the  emission  of 
light,  and  is  called  slow  combustion  or  decay.  The  heat  generated 
during  the  decay  of  a  substance  is  the  same  as  that  generated  by 
burning  the  substance ;  but  as  this  heat  is  liberated  in  the  first 
instance  during  weeks,  months,  or  perhaps  years,  its  generation  is  so 
slow  that  it  can  scarcely  be  noticed. 

No  organic  substance  found  or  formed  in  nature  contains  a  suffi- 
cient quantity  of  oxygen  to  cause  the  complete  combustion  of  the 
combustible  elements  (carbon  and  hydrogen)  present;  by  artificial 
processes  such  substances  may,  however,  be  produced,  and  are  then 
either  highly  combustible  or  even  explosive. 

During  common  combustion,  provided  an  excess  of  atmospheric  oxygen  be 
present,  the  total  quantity  of  carbon  is  converted  into  carbon  dioxide,  hydrogen 
into  water,  sulphur  and  phosphorus  into  sulphuric  and  phosphoric  acids,  while 
nitrogen  is  generally  liberated  in  the  elementary  state. 

During  the  process  of  decay  the  compounds  mentioned  above  are  produced 
finally,  although  many  intermediate  products  are  generated.  For  instance :  If 
a  piece  of  wood  be  burnt,  complete  oxidation  takes  place ;  intermediate  pro- 
ducts also  are  formed  chiefly  in  consequence  of  the  destructive  distillation  of 
a  portion  of  the  wood,  but  they  are  consumed  almost  as  fast  as  they  are  pro- 
duced, as  was  mentioned  in  connection  with  the  consideration  of  flame.  Again, 
when  a  piece  of  wood  is  exposed  to  the  action  of  the  atmosphere,  it  slowly 
burns  or  decays.  The  intermediate  products  formed  in  this  case  are  entirely 
different  from  those  produced  during  common  combustion. 

Common  alcohol  has  the  composition  C2H6O ;  in  burning,  it  requires 
six  atoms  of  oxygen,  when  it  is  converted  into  carbon  dioxide  and  water : 
C2H60     +     6O    =    2CO2    +    3II2O. 


292  CONSIDERATION  OF  CARBON  COMPOUNDS. 

But  alcohol  may  also  undergo  slow  oxidation,  in  which  case  oxygen 
first  removes  hydrogen,  with  which  it  combines  to  form  water,  whilst 
at  the  same  time  a  compound  known  as  acetic  aldehyde,  C2H4O,  is 

formed  : 

C2H60    +    O    =    C2H40    +    H20. 

This  aldehyde,  when  further  acted  upon   by  oxygen,  takes  up  an 
atom  of  this  element,  thereby  forming  acetic  acid : 

C2H4O    +    O    :  :    C2H402 

The  three  instances  given  above  illustrate  the  action  of  oxygen 
upon  organic  substances,  which  action  may  consist  in  a  mere  removal 
of  hydrogen,  in  a  replacement  of  hydrogen  by  oxygen,  or  in  an 
oxidation  of  both  the  carbon  and  hydrogen,  and  also  of  sulphur  and 
phosphorus,  if  they  be  present. 

An  organic  substance,  when  perfectly  dry  and  exposed  to  dry  air 
only,  may  not  suffer  decay  for  a  long  time  (not  even  for  centuries), 
but  in  the  presence  of  moisture  and  air  this  oxidizing  action  takes 
place  almost  invariably. 

Besides  the  slow  oxidation  or  decay  which  all  dead  organic  matter 
undergoes  in  the  presence  of  moisture,  there  is  another  kind  of  slow 
oxidation,  called  respiration,  which  takes  place  in  the  living  animal ; 
this  process  will  be  more  fully  considered  in  the  physiological  part  of 
this  book. 

Fermentation  and  putrefaction.  These  terms  are  applied  to 
peculiar  kinds  of  decomposition,  by  which  the  molecules  of  certain 
organic  substances  are  split  up  into  two  or  more  molecules  of  a  less 
complicated  composition.  These  decompositions  take  place  when 
three  factors  are  simultaneously  acting  upon  the  organic  substance. 
These  factors  are :  presence  of  moisture,  favorable  temperature,  and 
presence  of  a  substance  generally  termed  ferment. 

The  most  favorable  temperature  for  these  decompositions  lies 
between  25°  and  40°  C.  (77°  and  104°  F.),  but  they  may  take  place 
at  lower  or  higher  temperatures.  No  substance,  however,  will  either 
ferment  or  putrefy  at  or  below  the  freezing-point,  or  at  or  above  the 
boiling-point. 

The  nature  of  the  various  ferments  differs  widely,  and  their  true 
action  cannot,  in  many  cases,  be  explained ;  what  we  do  know  is, 
that  the  presence  of  comparatively  small  (often  minute)  quantities  of 
one  substance  (the  ferment)  is  sufficient  to  cause  the  decomposition  of 
large  quantities  of  certain  organic  substances,  the  ferment  itself  suf- 
fering often  no  apparent  change  during  this  decomposition.  Fer- 


DECOMPOSITION  OF  ORGANIC  COMPOUNDS.  293 

ments  may  be  divided  into  two  classes :  1.  Soluble  ferments,  which 
are  in  most  cases  nitrogenous  substances,  closely  related  to  the  pro- 
teids ;  2.  Living  micro-organisms  of  either  vegetable  or  animal  origin. 

The  nature  of  the  ferment  generally  determines  the  nature  of  the 
decomposition  which  a  substance  suffers,  or,  in  other  words,  one  and 
the  same  substance  will  under  the  influence  of  one  ferment  decom- 
pose with  liberation  of  certain  products,  while  a  second  ferment 
causes  other  products  to  be  evolved.  Sugar,  for  instance,  under  the 
influence  of  yeast,  is  converted  into  alcohol  and  carbon  dioxide, 
while  under  the  influence  of  certain  other  ferments  it  is  converted 
into  lactic  acid. 

The  difference  between  fermentation  and  putrefaction  is,  that  the 
first  term  is  used  in  those  cases  where  the  decomposing  substance 
contains  carbon,  hydrogen,  and  oxygen  only,  while  substances  con- 
taining, in  addition  to  these  three  elements,  either  nitrogen  or  sul- 
phur (or  both)  undergo  putrefaction.  The  two  last-named  elements 
are  generally  evolved  as  ammonia  or  derivatives  of  ammonia  and 
hydrogen  sulphide,  which  gases  give  rise  to  an  offensive  odor. 

Sugar,  having  the  composition  C6H12O6,  undergoes  fermentation, 
whilst  albuminous  substances  which  contain  also  nitrogen  and  sul- 
phur putrefy. 

The  oxygen  of  the  air  takes  no  part  in  either  fermentation  or 
putrefaction,  but  the  presence  or  absence  of  atmospheric  air  may 
cause  or  prevent  decomposition,  inasmuch  as  the  atmosphere  is  filled 
with  millions  of  minute  germs  of  organic  nature,  which  germs  may 
act  as  ferments  when  in  contact  with  organic  matter  under  favorable 
conditions. 

Whenever  organic  bodies  (a  dead  animal,  for  instance)  undergo  de- 
composition in  nature,  the  processes  of  fermentation  and  putrefaction 
are  generally  accompanied  by  oxidation  or  decay. 

The  conditions  under  which  a  substance  will  ferment  or  putrefy 
have  been  stated  above,  and  the  non-fulfilment  of  these  conditions 
enables  us  to  prevent  decomposition  artificially. 

Thus,  we  freeze  substances  (meat) ;  or  expel  all  water  from  or  dry 
them  (fruit,  etc.),  in  order  to  prevent  decomposition.  The  action  of 
the  ferments  is  counteracted  either  by  the  so-called  antiseptic  agents 
(salt,  carbolic  or  salicylic  acid,  etc.)  which  are  incompatible  with 
organic  life,  or  by  excluding  the  air,  and  with  it  the  ferments,  by 
enclosing  the  substances  in  air-tight  vessels  (glass  jars,  tin  cans,  etc.), 
which,  when  filled,  are  heated  sufficiently  to  destroy  any  germs  which 
may  have  been  present. 


294  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Antiseptics  and  disinfectants.  While  the  term  antiseptics  is 
applied  to  those  substances  which  retard  or  prevent  fermentation  and 
putrefaction,  the  term  disinfectants  refers  to  those  agents  actually 
destroying  the  organisms  which  are  the  causes  of  these  decomposi- 
tions. If  we  assume  that  all  infectious  diseases  are  due  to  micro- 
organisms, or  germs  of  various  kinds,  disinfectants  may  be  considered 
as  equivalent  to  germicides.  Disinfectants  are  generally  antiseptics 
also,  but  the  latter  are  not  in  all  cases  disinfectants.  The  solution 
of  a  substance  of  certain  strength  may  act  as  a  disinfectant  and 
antiseptic,  while  the  same  solution  diluted  further  may  act  as  an 
antiseptic  only,  but  not  as  a  disinfectant. 

Deodorizers  are  those  substances  which  convert  the  strongly  smell- 
ing products  of  decomposition  into  inodorous  compounds.  Strong 
oxidizing  agents  are  generally  good  deodorizers,  as,  for  instance, 
chlorine,  potassium  permanganate,  hydrogen  dioxide,  etc.  Among 
the  best  antiseptics  and  disinfectants  are  chlorine  (generally  used  in 
the  form  of  a  4  per  cent,  solution  of  hypochlorite  of  calcium),  mer- 
curic chloride  (a  solution  of  1  :  500  or  1  : 1000),  carbolic  acid  (a  5  per 
cent,  solution),  and  some  other  substances. 

Action  of  chlorine  and  bromine.  These  two  elements  act  upon 
organic  substances  (similarly  to  oxygen)  in  three  different  ways,  viz., 
they  either  (rarely,  however)  combine  directly  with  the  organic  sub- 
stance, or  remove  hydrogen,  or  replace  hydrogen.  The  following 
equations  illustrate  this  action  : 

C2H4        +         2Br  C2H4Br2. 

Ethylene.  Bromine.          Ethylene  bromide. 

C2H6O      +      2C1    :   :    C2H40      +      2HC1. 
Ethyl  alcohol.       Chlorine.      Aldehyde.    Hydrochloric  acid. 

C2H4O2      +      2C1  C2H3C102      +      HC1. 

Acetic  acid.         Chlorine.       Monochloracetic      Hydrochloric 

acid.  acid. 

In  the  presence  of  water,  chlorine  and  bromine  often  act  as  oxidiz- 
ing agents  by  combining  with  the  hydrogen  of  the  water  and  liber- 
ating oxygen ;  iodine  may  act  in  a  similar  manner  as  an  oxidizing 
agent,  but  it  rarely  acts  directly  by  substitution. 

Action  of  nitric  acid.  This  substance  acts  either  by  direct  com- 
bination with  organic  bases  forming  salts,  or  as  an  oxidizing  agent, 
or  by  substitution  of  nitryl,  NO2,  for  hydrogen.  As  instances  of  the 


DECOMPOSITION  OF  ORGANIC  COMPOUNDS.  295 

latter  action  may  be  mentioned  the  formation  of  nitro-benzene  and 
nitre-cellulose  : 

C6H6    +     HN03    =    C6H5N02    -f     H2O. 
Benzene.       Nitric  acid.       Nitrobenzene.         Water. 

C6H1005    +    3HN03    =    C6H7(N02)305    +     3H2O. 
Cellulose.          Nitric  acid.         Trinitro-cellulose.  Water. 

The  additional  quantity  of  oxygen  thus  introduced  into  the  mole- 
cules renders  them  highly  combustible,  or  even  explosive. 

Action  of  dehydrating-  agents.  Substances  having  a  great 
affinity  for  water,  such  as  strong  sulphuric  acid,  phosphoric  oxide, 
and  others,  act  upon  many  organic  substances  by  removing  from  them 
the  elements  of  hydrogen  and  oxygen,  and  combining  with  the  water 
formed,  while,  at  the  same  time,  frequently  dark  or  even  black  com- 
pounds are  formed,  which  consist  largely  of  carbon.  The  black 
color  imparted  to  sulphuric  acid  by  organic  matter  depends  on  this 
action. 

Action  of  alkalies.  The  hydroxides  of  potassium  and  sodium 
act  in  various  ways  on  organic  substances. 

In  some  cases  direct  combination  takes  place  : 

CO        +        KOH        ==       KCHO2. 
Carbonic  oxide.         Potassium  Potassium 

hydroxide.  formate. 

Salts  are  formed : 

C2H402    +    NaOH  s=  NaC2H3O2     +     H2O. 
Acetic  Sodium  Sodium  Water, 

acid.  hydroxide.          acetate. 

Fats  are  decomposed  with  the  formation  of  soap  : 

C3H5(C18H3302)3    4-    3NaOH       :    C3H5(HO)3    -f     3NaC18H33O2. 
Oleate  of  glyceril.     Sodium  hydroxide.        Glycerin.  Sodium  oleate. 

Oxidation  takes  place,  while  hydrogen  is  liberated  : 

C2H60     +     KOH  KC2H302     +    4H. 

Ethyl  Potassium  Potassium          Hydrogen, 

alcohol.          hydroxide.  acetate. 

From  compounds  containing  nitrogen,  ammonia  is  evolved : 

NH2C2H3O    +    KOH  KC2H3O2     +    NH3. 

Acetamide.  Potassium          Potassium          Ammonia, 

hydroxide.  acetate. 

Action  of  reducing-  agents.  Deoxidizing  or  reducing  agents, 
especially  hydrogen  in  the  nascent  state,  act  upon  organic  substances 
either  by  direct  combination  : 

C2H40        +        2H  C.2H60. 

Ethene  oxide.  Ethyl  alcohol. 


296  CONSIDERATION  OF  CARBON  COMPOUNDS. 

or  by  removing  oxygen  (and  also  chlorine  or  bromine)  : 

C7H602    +    2H       :    C7H60     +    H20. 
Benzole  acid.  Benzole  aldehyde. 

In  some  cases  hydrogen  replaces  oxygen  : 


C6H5N02     +     6H    =    C6H5NH2     +     2H2O. 
Nitro-benzene.  Aniline. 

Classification  of  organic  compounds.  There  are  great  diffi- 
culties in  arranging  the  immense  number  of  organic  substances 
properly,  and  in  such  a  manner  that  natural  groups  are  formed  the 
members  of  which  are  similar  in  composition  and  possess  like 
properties. 

Various  modes  of  classification  have  been  proposed,  some  of  which, 
however,  are  so  complicated  that  the  beginner  will  find  it  difficult  to 
make  use  of  them.  The  grouping  of  organic  substances  here  adopted, 
while  far  from  being  perfect,  has  the  advantages  of  being  simple, 
easily  understood,  and  remembered. 

1.  Hydrocarbons.     All  compounds   containing  the  two  elements 
carbon  and  hydrogen  only.     For  instance,  CH4,  C6H6,  C10H16,  etc. 

2.  Alcohols.     These  are  unsaturated  hydrocarbons  or  hydrocarbon 
residues  in  combination  with  hydroxyl,  OH.     For  instance,  ethyl 
alcohol,  C2IT5OH,  glycerin,  C,Wli5  (OH)3,  etc. 

3.  Aldehydes.     Unsaturated  hydrocarbons  in  combination  with  the 
radical  COH  ;  they  are  compounds  intermediate  between  alcohols 
and  acids,  or  alcohols  from  which  hydrogen  has  been  removed.     For 
instance  : 

C2HeO,  C2H40,  C2H402- 

Ethyl  alcohol.  Aldehyde.  Acetic  acid. 

4.  Organic   acids.      Unsaturated    hydrocarbons   in    combination 
with  carboxyl,  a  radical  having  the  composition   CO2H,  or  com- 
pounds formed   by  replacement  of  hydrogen  in  hydrocarbons   by 
carboxyl.      Instances  :   Acetic   acid,  CH3CO2H  ;   pyrotartaric  acid 
C3H6(C02H)2. 

5.  Ethers.     Compounds  formed  from  alcohols  by  replacement  of 
the  hydrogen  of  the  hydroxyl  by  other  unsaturated  hydrocarbons,  or, 
what  is  the  same,  by  other  alcohol  radicals.     For  instance  : 


'  C2H5x'  C  H3/> 

Ethyl  alcohol.  Ethyl  ether.          Ethyl-methyl  ether. 

6.   Compound  ethers  or  esters.     Formed  from  alcohols  by  replace- 
ment of  the  hydrogen  of  the  hydroxyl  by  acid  radicals,  or  from  acids 


CLASSIFICATION  OF  ORGANIC  COMPOUNDS.  297 

by  replacement  of  the  hydrogen  of  carboxyl  by  alcohol  radicals. 
For  instance : 

C2H5\0        CH3CO\0  C2H5\0     ,    H\0 

H/C  H/C     =  CH3CO/C      ~  H/C 

Ethyl  alcohol.        Acetic  acid.  Acetic  ether.          Water. 

The  various  fats  belong  to  this  group  of  compound  ethers. 

7.  Carbohydrates.     (Sugars,  starch,  cellulose,  etc.)      These  com- 
pounds contain  6  atoms  of  carbon  (or  a  multiple  of  6)  in  the  molecule, 
and  hydrogen  and  oxygen  in  the  proportion  of  2  atoms  of  hydrogen 
to  1   atom  of  oxygen,  or  in  the  proportion  to  form  water.     Most 
carbohydrates  are  capable  of  fermentation,  or  of  being  easily  con- 
verted into  fermentable  bodies.     Instances  :  C6H12O6,  C6H10O5,  etc. 

Glucosides  are  substances  the  molecules  of  which  may  be  split  up 
in  such  a  manner  that  several  new  bodies  are  formed,  one  of  which 
is  sugar. 

8.  Amines  and   amides.     Substances   formed   by   replacement   of 
hydrogen  in  ammonia  by  alcohol  or  acid  radicals.     For  instance : 
ethyl  amine,  NH2.C2H5,  urea,  N2H4.CO,  etc.     The  alkaloids  belong 
to  this  group. 

9.  Cyanogen  and  its  compounds.    Substances  containing  the  radical 
cyanogen,  CN.     For  instance  :  potassium  cyanide,  KCN. 

10.  Proteids   or   albuminous  substances.      These,    besides   carbon, 
hydrogen,  and  oxygen,  always  contain  nitrogen  and  sulphur,  some- 
times also  other  elements.     Instances :  albumin,  casein,  fibrin,  etc. 

In  connection  with  each  of  these  groups  have  to  be  considered  the 
derivatives  obtained  from  them  directly  or  indirectly. 

As  all  those  organic  compounds  the  constitution  of  which  has 
been  explained  may  be  looked  upon  as  derivatives  of  either  methane, 
CH4,  or  benzene,  C6H6,  a  separation  of  organic  compounds  is  made 
into  two  large  classes,  each  one  embodying  all  the  derivatives  of  one 
of  the  two  hydrocarbons  named.  The  derivatives  of  methane  are 
termed  fatty  compounds,  those  of  benzene  aromatic  compounds.  Fatty 
compounds  have  representatives  in  each  one  of  the  above  ten  groups : 
aromatic  compounds  are  missing  in  a  few.  As  far  as  practicable,  the 
two  classes  will  be  considered  separately,  because  the  properties  of 
fatty  and  aromatic  compounds  differ  so  widely,  in  some  respects,  that 
this  method  of  studying  the  nature  of  carbon  compounds  is  to  be 
preferred. 

QUESTIONS.— 381.  Explain  the  term  residue  or  radical.  382.  What  is  under- 
stood by  the  expression  chain,  when  used  in  chemistry  ?  383.  What  are  the 
characteristics  of  an  homologous  series?  384.  Give  an  explanation  of  the 


298  CONSIDERATION  OF  CARBON  COMPOUNDS. 

40.   HYDEOCAEBONS. 

Occurrence  in  nature.  Hydrocarbons  are  seldom  derived  from 
animal  sources,  being  more  frequently  products  of  vegetable  life; 
thus,  the  various  essential  oils  (oil  of  turpentine  and  others)  of  the 
composition  C10H16  or  C20H32  are  frequently  found  in  plants,  where 
they  are  formed  from  carbon  dioxide  and  water : 

10C02     +     8H20        :    C10H16    +    280. 

This  equation,  whilst  showing  the  possibility  of  the  formation  of 
an  essential  oil  in  the  plant,  must  not  be  taken  to  mean  that  10 
molecules  of  carbon  dioxide  and  8  molecules  of  water  are  simultane- 
ously decomposed,  with  the  production  of  a  hydrocarbon;  on  the 
contrary,  we  know  that  many  intermediate  substances  are  formed, 
and  the  formula  simply  gives  the  final  result,  not  the  intermediate 
stages  of  the  process. 

Other  hydrocarbons  are  found  in  nature  as  products  of  the  decom- 
position of  organic  matter.  Thus  methane,  CH4,  is  generally  formed 
during  the  decay  of  organic  matter  in  the  presence  of  moisture ;  the 
higher  members  of  the  methane  series  are  found  in  crude  coal-oil. 

Formation  of  hydrocarbons.  It  is  difficult  to  combine  the  two 
elements  carbon  and  hydrogen  directly ;  as  an  instance  of  such  direct 
combination  may  be  mentioned  acetylene,  C2H2,  which  is  formed 
when  electric  sparks  pass  between  electrodes  of  carbon  in  an  atmos- 
phere of  hydrogen. 

Many  hydrocarbons  are  obtained  by  destructive  distillation  of 
organic  matter,  and  their  nature  depends  on  the  composition  of  the 
material  used  and  upon  the  degree  of  heat  applied  for  the  decompo- 
sition. Hydrocarbons  may  also  be  obtained  by  the  decomposition 
(other  than  destructive  distillation)  of  numerous  organic  bodies,  such 
as  alcohols,  acids,  amines,  etc.,  and  from  derivatives  of  these  sub- 
stances. 

The  hydrocarbons  found  in  nature  are  generally  separated  from 
other  matter,  as  well  as  from  each  other,  by  the  process  known  as 

terms  isomerism,  metamerism,  and  polymerism.  385.  How  does  heat  act  upon 
organic  compounds?  386.  What  is  destructive  distillation?  387.  State  the 
difference  between  combustion,  decay,  fermentation,  and  putrefaction ;  what  is 
the  nature  of  these  processes,  and  under  what  conditions  do  they  take  place  ? 

388.  How  do  chlorine,  nitric  acid,  and  alkalies  act  upon  organic  substances? 

389.  What  is  the  action  of  hydrogen,  and  of  dehydrating  agents,  upon  organic 
substances  ?     390.  Mention  the  chief  groups  of  organic  compounds. 


HYDROCARBONS. 


299 


fractional  distillation.  As  the  boiling-points  of  the  various  compounds 
differ  more  or  less,  they  may  be  separated  by  carefully  distilling  off 
the  compounds  of  lower  boiling-points,  while  noting  the  temperature 
of  the  vapors  above  the  boiling  liquid  by  means  of  an  inserted  ther- 
mometer, and  changing  the  receiver  every  time  an  increase  of  the 
boiling-point  is  noticed.  This  separation  of  volatile  liquid,  known 
as  fractional  distillation,  is,  however,  not  absolutely  complete,  because 
traces  of  substances  having  a  higher  boiling-point  are  simultaneously 
volatilized  with  the  distilling  substance. 


FIG.  39. 


Flasks  arranged  for  fractional  distillation. 


For  fractional  distillation  of  small  quantities  of  liquids  as  well  as 
for  the  determination  of  boiling-points,  flasks  arranged  like  those 
shown  in  Fig.  39  may  be  used. 

Properties  of  hydrocarbons.  There  are  no  other  two  elements 
which  combine  together  in  so  many  proportions  as  carbon  and  hydro- 
gen. Several  hundred  hydrocarbons  are  known,  many  of  which 
form  either  homologous  series  or  are  metameric  or  polymeric. 

Hydrocarbons  occur  either  as  gases,  liquids,  or  solids.  If  the  mole- 
cule contains  not  over  4  atoms  of  carbon,  the  compound  is  generally 


300  CONSIDERATION  OF  CARBON  COMPOUNDS 

a  gas  at  the  ordinary  temperature ;  if  it  contains  from  4  to  10  or  12 
atoms  of  carbon,  it  is  a  liquid ;  and  if  it  contains  a  yet  higher  number 
of  carbon  atoms,  it  is  generally  a  solid. 

All  hydrocarbons  may  be  volatilized  without  decomposition,  all 
are  colorless  substances,  and  many  have  a  peculiar  and  often  charac- 
teristic odor ;  they  are  generally  insoluble  in  water  but  soluble  in 
alcohol,  ether,  disulphide  of  carbon,  etc. 

In  regard  to  chemical  properties,  it  may  be  said  that  hydrocarbons 
are  neutral  substances,  behaving  rather  indifferently  toward  most 
other  chemical  agents.  Most  of  them  are,  however,  oxidized  by  the 
oxygen  of  the  air,  by  which  process  liquid  hydrocarbons  are  often 
converted  into  solids. 

Hydrocarbons  of  the  paraffin  or  methane  series.  The  hydro- 
carbons having  the  general  composition  CnH2n  +  2  are  known  as 
paraffins,  the  name  being  derived  from  the  higher  members  of  the 
series  which  form  the  paraffin  of  commerce.  The  following  table 
gives  the  composition,  boiling-points,  etc.,  of  the  first  sixteen  mem- 
bers of  this  series : 

B.  P.  Sp.  gr. 

Methyl  hydride  or  methane,  C  H4   \ 

Ethyl  hydride  or  ethane,  C2  H6    I  gases. 

Propyl  hydride  or  propane,  C3  H8   J 

Butyl  hydride  or  butane,  C4  H10  1°  C. 

Amyl  hydride  or  pentane,  C5  H12  38  0.628 

Hexyl  hydride  or  hexane,  C6  Hu  70  0.669 

Heptyl  hydride  or  heptane,  C7  H16  99  0.690 

Octyl  hydride  or  octane,  C8  H18  125  0.726 

Nonyl  hydride  or  nonane,  C9  H20  148  0.741 

Decyl  hydride  or  decane,  C10H22  166  0.757 

Undecyl  hydride  or  undecane,  CnH24  184  0.766 

Dodecyl  hydride  or  dodecane,  C12H26  202  0.778 

Tridecyl  hydride  or  tridecane,  C13H28  218  0.796 

Tetradecyl  hydride  or  tetradecane,  CUH30  236  0.809 

Pentadecyl  hydride  or  pentadecane,  ClgH32  258  0.825 

Hexadecyl  hydride  or  hexadecane,  C16H34  280 
etc. 

The  above  table  shows  that  the  paraffins  form  an  homologous 
series ;  the  first  four  members  are  gases,  most  of  the  others  liquids, 
regularly  increasing  in  specific  gravity,  boiling-point,  viscidity,  and 
vapor  density,  as  their  molecular  weight  becomes  greater. 

The  paraffins  are  saturated  hydrocarbons,  the  constitution  of  which 
has  been  already  explained;  they  are  incapable  of  uniting  directly 
with  monatomic  elements  or  residues,  but  they  easily  yield  sub- 


HYDROCARBONS.  301 

stitution-derivatives   when   subjected   to  the  action  of  chlorine  or 
bromine. 

Most  of  the  paraffins  are  known  in  two  (or  even  more)  modifications ;  there 
are,  therefore,  other  homologous  series  of  hydrocarbons  of  the  same  composition 
as  the  above  normal  paraffins,  which  show  some  difference  from  the  normal 
paraffins  in  boiling-points  and  other  properties.  In  these  isomeric  paraffins  the 
atoms  are  arranged  differently  from  those  in  the  normal  hydrocarbons,  which 
fact  may  be  proven  by  the  difference  in  decomposition  which  these  substances 
suffer  when  acted  upon  by  chemical  agents. 

No  isomeric  hydrocarbons  of  the  first  three  members  of  the  paraffin  series  are 
known,  which  fact  is  in  accordance  with  our  present  theories.  Assuming  that 
the  quadrivalent  carbon  atoms  exert  their  full  valence,  and  that  they  are  held 
together  by  one  atomicity  only,  we  can  arrange  the  atoms  in  the  compounds, 
CH4,  C2H6,  and  C3H8,  not  otherwise  than  thus  : 

TT  O^^-LiQ 

CEEH3  | 

^1  U. 


C H3 


In  the  next  compound,  butane,  C4H10,  we  have  two  possibilities  explaining 
the  structure  of  the  molecule,  namely,  these  : 


C=H2  C=H3 

C=H2  C=H3—  CH-CEEH3. 

C=H3 

Both  these  compounds  are  known,  and  termed  normal  butane  and  isobutane, 
respectively. 

The  next  member,  pentane,  C5H12,  shows  three  possibilities  of  constitution, 
thus  : 


3 

U 
* 


I  C=H3 

—  H. 

C^H3—  C—  CEEH. 


H2 

C=H2 

0=H2  | 

I  C=H3 

C£EH3 

These  compounds  also  are  known.  With  the  higher  members  of  the  paraffins 
tne  number  of  possible  isomeres  rises  rapidly  according  to  the  law  of  permuta- 
tion, so  that  we  have  of  the  seventh  member  9,  of  the  tenth  75,  and  of  the 
thirteenth  member  799,  possible  isomeric  hydrocarbons. 

Methane,  CH4  (Marsh-gas,  Fire-damp).  This  hydrocarbon  has 
been  spoken  of  in  Chapter  13,  where  it  was  stated  that  it  is  a  color- 
less, combustible  gas,  which  is  formed  by  the  decay  of  organic  matter 
in  the  presence  of  moisture,  during  the  formation  of  coal  in  the 


302  CONSIDERATION  OF  CARBON  COMPOUNDS. 

interior  of  the  earth,  and  by  the  destructive  distillation  of  various 
organic  matters.  Methane  is  of  special  interest,  because  it  is  the 
compound  from  which  thousands  of  other  substances  are  derived.  It 
may  be  made  by  the  action  of  inorganic  substances  upon  one  another; 
for  instance,  by  passing  a  mixture  of  steam  and  carbon  disulphide 
over  copper  heated  to  red  heat,  when  the  following  change  takes 

place  : 

6Cu  +  CS2  +  2H20  =  2Cu2S  +  2CuO  +  CH4 

Bearing  in  mind  that  carbon  disulphide,  as  well  as  water,  may  be 
obtained  by  direct  union  of  the  elements,  it  is  evident  that  methane 
may  be  formed  indirectly,  by  means  of  the  above  method,  from  the 
elements  carbon  and  hydrogen. 

Experiment  40.  Use  apparatus  shown  in  Fig.  5,  page  37,  omitting  the  bent 
tube  B.  Mix  in  a  mortar  20  grammes  of  sodium  acetate  with  20  grammes  of 
potassium  (or  sodium)  hydroxide  and  30  grammes  of  calcium  hydroxide  ;  fill 
with  this  mixture  the  tube  A,  which  should  be  made  of  glass  fusing  with 
difficulty,  or  of  so-called  "combustion  tubing;"  apply  heat  and  collect  the  gas 
over  water.  The  decomposition  takes  place  thus  : 

NaC2H3O2  -f-  NaOH  =a  Na2CO3  -f  CH4. 

Ignite  the  gas,  and  notice  that  its  flame  is  but  slightly  luminous.  Mix  some 
of  the  gas  in  a  wide-mouth  cylinder,  of  not  more  than  about  200  c.c.  capacity, 
with  an  equal  volume  of  air  and  ignite.  Eepeat  this  experiment  with  mixtures 
of  one  volume  of  methane  with  2,  4,  6,  8,  and  10  volumes  of  atmospheric  air. 
Which  mixture  is  most  explosive,  and  why  ?  How  many  volumes  of  oxygen 
and  how  many  volumes  of  atmospheric  air  are  needed  for  the  complete  com- 
bustion of  one  volume  of  methane  ? 

Coal.  As  methane  is  one  of  the  products  generated  during  the 
formation  of  coal,  it  may  be  well  to  consider  this  process  here  briefly. 

The  various  substances  classed  togther  under  the  name  of  coal  con- 
sist principally  of  carbon,  associated  with  smaller  quantities  of  hydro- 
gen, oxygen,  nitrogen,  sulphur,  and  certain  inorganic  mineral  matters 
which  compose  the  ash.  Coal  is  formed  from  buried  vegetable 
matter  by  a  process  of  decomposition  which  is  partly  a  fermentation, 
partly  a  decay,  and  chiefly  a  slow  destructive  distillation,  the  heat 
for  this  latter  process  being  derived  from  the  interior  of  the  earth,  or 
by  the  decomposition  itself. 

The  principal  constituent  of  the  organic  matter  furnishing  coal  is 
wood  (or  woody  fibre,  cellulose),  and  a  comparison  of  the  composition 
of  this  substance  with  the  various  kinds  of  coal  gradually  formed 
will  help  to  illustrate  the  chemical  change  taking  place  : 


HYDROCARBONS.  303 

Carbon.  Hydrogen.  Oxygen. 

Wood 100  12.18  83.07 

Peat 100  9.85  55.67 

Lignite 100  8.37  42.42 

Bituminous  coal         .        .        .        .100  6.12  21.23 

Anthracite  coal 100  2.84  1.74 

This  table  shows  a  progressive  diminution  in  the  proportions  of 
hydrogen  and  oxygen  during  the  passage  from  wood  to  anthracite. 
These  two  elements  must,  therefore/  be  eliminated  in  some  form  of 
combination  which  allows  them  to  move,  viz.,  as  gases  or  liquids. 
The  gases  formed  are  chiefly  carbon  dioxide  (which  finds  its  way 
through  the  rocks  and  soils  to  the  surface  either  in  the  gaseous  state 
or  after  having  been  absorbed  by  water  in  the  form  of  carbonic  acid 
springs)  and  methane,  known  to  coal-miners  as  fire-damp,  frequently 
causing  the  formation  of  explosive  gas  mixtures  in  the  coal  mines,  or 
escaping,  like  carbon  dioxide,  through  fissures  to  the  surface  of  the 
earth,  where  it  may  be  ignited. 

Natural  gas.  While  methane  and  other  combustible  gases  are 
undoubtedly  formed  during  the  formation  of  coal,  the  gas  mixture 
now  generally  termed  natural  gas  (a  mixture  of  methane,  ethane, 
propane,  hydrogen,  and  a  few  other  gases),  and  used  largely  for 
heating  and  illuminating  purposes,  is  most  likely  a  product  of  the 
complete  decomposition  of  vegetable  and  animal  matter  which  has 
been  precipitated  from  water,  simultaneously  with  inorganic  matter, 
during  the  formation  of  certain  rocks,  chiefly  slate  and  limestone. 
The  decomposition  of  this  organic  matter  has  been  so  complete  that 
the  gaseous  decomposition-products  only  are  left,  but  no,  or  very 
little  of,  solid  residue  similar  to  coal. 

Coal-oil,  Petroleum.  Similar  to  natural  gas,  coal-oil  is  a  product 
of  the  decomposition  of  organic  matter,  most  likely  of  the  fats  and 
oils  of  fish  and  other  aquatic  animals.  While  the  albuminous  con- 
stituents of  dead  animal  matter  decompose  rapidly,  fats  are  compara- 
tively stable.  These  oils  and  fats,  after  being  precipitated  simul- 
taneously with  other  organic  and  inorganic  matter  from  water,  have 
formed  by  their  decomposition  (which  was  chiefly  a  destructive  dis- 
tillation) the  liquid  we  call  coal-oil  or  petroleum. 

Coal-oil  is  a  mixture  of  the  various  liquid  paraffins,  containing 
often  in  solution  the  gaseous  and  solid  members  of  this  group,  as  also 
small  quantities  of  coloring  and  other  matter.  The  boiling-points  of 
the  constituents  of  coal-oil  lie  between  0°  and  300°  C.  (32°  and 


304  CONSIDERATION  OF  CARBON  COMPOUDDS. 

572°  F.),  or  even  higher.  The  crude  oil  is  purified,  by  treating  it 
with  sulphuric  acid,  followed  by  other  processes  of  refining,  and 
finally  by  fractional  distillation,  in  order  to  separate  the  members  of 
low  boiling-points  from  those  of  higher  boiling-points. 

The  hydrocarbons  of  low  boiling-points,  chiefly  a  mixture  of  C5H12 
and  C6H14,  are  official,  under  the  name  of  benzin  or  petroleum-ether, 
which  name  must  not  be  confounded  with  benzene  or  benzol,  C6H6. 
According  to  the  U.  S.  P.,  benzin  should  have  a  specific  gravity  from 
0.67  to  0.675,  and  a  boiling-point  of  50°  to  60°  C.  (122°  to  140°F.). 

Other  similar  liquids  are  sold  in  the  market  under  the  name  of 
rhigoline,  B.  P.  about  2r°C.  (70°  F.)  and  gasoline,  B.  P.  about  75° 
€.  (167°  F.) ;  they  are  highly  inflammable. 

The  paraffins  distilling  between  150°  and  250°  C.  (302°  and  408° 
F.)  constitute  the  common  illuminating  oil,  various  kinds  of  which  are 
sold  as  kerosene,  paraffin  oil,  astral  oil,  mineral  sperm  oil,  etc.  The 
danger  which  arises  in  the  use  of  coal-oil  as  an  illuminating  agent 
is  caused  by  the  use  of  oils  which  have  not  been  sufficiently  freed 
from  the  more  volatile  members  of  the  series,  which,  when  but 
slightly  heated  (or  even  at  ordinary  temperature)  will  vaporize,  and 
upon  mixing  with  atmospheric  air,  form  explosive  mixtures.  An  oil 
to  be  safely  used  for  illuminating  purposes  in  common  lamps  should 
not  give  off  inflammable  vapors  (or  flash)  below  49°  C.  (120°  F.). 

Experiment  41.  Various  forms  of  apparatus  are  used  for  the  exact  determi- 
nation of  the  flashing-point;  students  may  determine  it  approximately  by 
operating  as  follows :  Fill  a  cylinder  (about  one  inch  in  diameter  and  six 
inches  high)  two-thirds  with  coal-oil,  suspend  in  the  oil  a  thermometer,  place 
the  cylinder  in  a  vessel  with  water  (water-bath),  keeping  the  level  of  the  oil 
even  with  that  of  the  water,  and  heat  the  latter  slowly.  Cover  the  cylinder 
loosely  with  a  piece  of  pasteboard,  and  when  the  thermometer  indicates  a  rise 
in  temperature  pass  a  small  flame  quickly  over  the  mouth  of  the  cylinder  after 
having  removed  the  pasteboard.  Repeat  this  operation,  from  degree  to  degree, 
until  a  bluish  flame  is  noticed  running  down  to  the  surface  of  the  oil.  The 
temperature  at  which  this  takes  place  indicates  the  flashing-point. 

After  the  illuminating  oil  has  been  distilled  off,  a  mixture  of  sub- 
stances passes  over,  which  is  used  for  lubricating  purposes  or  furnishes, 
after  having  been  purified  by  treatment  with  bone-black,  the  official 
articles  known  as  soft  and  hard  petrolatum.  Both  are  fat-like  masses, 
more  or  less  fluorescent,  varying  in  color  from  white  to  yellowish  or 
yellow,  and  almost  without  odor  or  taste.  The  article  sold  as  vaseline 
is  practically  identical  with  soft  petrolatum. 

Liquid  petrolatum  of  the  U.  S.  P.  is  a  petroleum  of  a  specific 
gravity  0.875  to  0.945. 


HYDROCARBONS. 


305 


A  mixture  of  the  highest  and  solid  members  of  the  paraffin  series 
distilling  at  a  temperature  about  350°  C.  (662°  F.)  is  known  as 
paraffin,  a  white,  crystalline  substance  used  for  candles,  etc. ;  it  fuses 
at  about  75°  C.  (167°  F.). 

Illuminating-  gas  is  a  mixture  of  gases  obtained  by  the  destructive 
distillation  of  coal  (or  wood)  in  iron  retorts,  with  subsequent  purifica- 
tion of  the  gases  generated.  The  constituents  of  coal  have  been  men- 
tioned above.  The  products  formed  from  it  during  its  destructive 
distillation  are  very  numerous  ;  the  following  are  the  most  important: 


f  Hydrogen       .                  . 

.    H. 

Methane 

.    CH4. 

Ethene  .... 

C9H,. 

Acetylene 

.    C2H2. 

Gases 

Nitrogen 

.    N. 

Ammonia 

.    NH3. 

Carbonic  oxide 

.     CO. 

Carbon  dioxide 

.    CO2. 

Hyclrosulphuric  acid 

.    H2S. 

I  Hydrocyanic  acid  . 

.    HCN. 

B.  P. 

f  Benzene 

.    C6H6 

80° 

Toluene 

•    C7H8 

110 

f  Liquids     -{   Aniline  .... 

.    C6H5NH2 

132 

Acetic  acid     . 

.    C2H402 

117 

Coal-tar^                       Water    •        •        •        • 

.    H2O 

100 

Carbolic  acid 

.    C6H60 

188 

Kresylic  acid 

.    C7H80 

201 

.  Solids 

Naphtalene    . 

•    C10H8 

220 

Anthracene    . 

.    CUH10 

360 

Paraffin. 

•    C16H34 

280 

Solid  residue  :  Coke,  chiefly  carbon  and  inorganic  matter. 

The  gases  are  purified  by  condensing  ammonia  (and  some  other 
gases)  in  water,  carbon  dioxide  and  hydrosulphuric  acid  in  calcium 
hydroxide.  The  following  is  the  composition  of  a  purified  illumi- 
nating gas  obtained  from  cannel-coal : 

Hydrogen 46  volumes. 

Methane 41         " 

Ethene 6        " 

Carbonic  oxide 4         " 

Carbon  dioxide 2         " 

Nitrogen 1  volume. 

Experiment  42.  Use  apparatus  shown  in  Fig.  5,  page  37.  Fill  the  combus- 
tion-tube A  with  sawdust  (almost  any  other  non-volatile  organic  matter  may  be 
used),  apply  heat  and  continue  it  as  long  as  gases  are  evolved.  Notice  that  by 
this  process  of  destructive  distillation  are  formed  a  gas  (or  gas  mixture),  which 

20 


306  CONSIDERATION  OF  CARBON  COMPOUNDS. 

may  be  ignited,  a  dark,  almost  black  liquid  (tar),  which  condenses  in  the  tube 
B,  and  that  a  residue  is  left  which  is  chiefly  carbon.  The  tarry  liquid  shows  an 
acid  reaction,  due  to  acetic  and  other  acids  present. 

Coal-tar,  obtained  as  a  by-product  in  the  manufacture  of  illumi- 
nating gas,  contains,  as  shown  by  the  above  table,  many  valuable  sub- 
stances, such  as  benzene,  aniline,  carbolic  acid,  paraffin,  etc.,  which 
are  separated  from  each  other  by  making  use  of  the  difference  in  their 
boiling-points  and  specific  gravities,  or  of  their  solubility  or  insolu- 
bility in  various  liquids,  or,  finally,  of  their  basic,  acid,  or  neutral 
properties. 

defines.  The  hydrocarbons  of  the  general  formula  CnH2n  are 
termed  olefines.  To  this  series  belong  : 

Ethene  or  ethylene    .         .  .         .  C2H4. 

Propene  or  propylene         ....  C3H6. 

Butene  or  butylene C4H8. 

Pentene  or  amylene C5H10. 

Hexene  or  hexylene C6H12. 

Methene,  CH2,  the  lowest  term  of  this  series,  is  not  known.  The 
hydrocarbons  of  this  series  are  not  only  homologous,  but  also  poly- 
meric with  one  another. 

Of  special  interest  is  the  first  known  member  of  the  series,  ethene  or 
oleftant  gas,  on  account  of  its  normal  occurrence  in  illuminating  gas, 
as  well  as  in  most  common  flames,  the  luminosity  of  which  depends 
greatly  on  the  quantity  of  this  compound  present  in  the  burning  gas. 

Benzene  series,  or  aromatic  hydrocarbons.  The  members  of  a 
series  of  hydrocarbons  having  the  general  composition  CJET2  -6,  and 
all  the  derivatives  of  this  group,  including  the  alcohols,  acids,  etc.,  are 
the  substances  spoken  of  before  as  aromatic  compounds,  and  will  be 
considered  later. 

Volatile  or  essential  oils.  The  term  essential  oil  is  more  a  phar- 
maceutical than  chemical  term,  and  is  used  for  a  large  number  of 
liquids  obtained  from  plants,  and  having  in  common  the  properties 
of  being  volatile,  soluble  in  ether  and  alcohol,  almost  insoluble  in 
water,  and  having  a  distinct  and  in  most  cases  even  highly  character- 
istic odor.  They  stain  paper  as  do  fats  or  fat  oils,  from  which  they 
differ,  however,  by  the  disappearance  after  some  time  of  the  stain 
produced,  while  fats  leave  a  permanent  stain. 

In  their  chemical  composition  essential  oils  differ  widely ;  some 


ALCOHOLS.  307 

are  compound  ethers,  others  aldehydes,  but  most  of  them  are  hydro- 
carbons or  oxidized  hydrocarbons,  belonging  to  the  benzene-deriva- 
tives, where  they  will  be  considered. 

41.    ALCOHOLS. 

Constitution  of  alcohols.  The  old  term  "alcohol"  originally 
indicated  but  one  substance  (ethyl  alcohol),  but  is  now  applied  to  a 
large  group  of  substances  which  may  be  looked  upon  as  being  derived 
from  hydrocarbons  by  replacement  of  one,  two,  or  more  hydrogen 
atoms  by  hydroxyl,  OH. 

Any  hydrocarbon  may  be  converted  jnto  an  alcohol  radical  by 
removal  of  one  or  more  hydrogen  atoms  ;  methane,  CH4,  for  instance, 
is  converted  into  methyl,  CH3,  which,  upon  combining  with  hydroxyl, 
forms  methyl  alcohol,  CH3OH. 

It  has  been  shown  before  that  the  higher  members  of  the  paraffin  series  are 
capable  of  forming  a  number  of  isomeric  compounds.  Eunning  parallel  to  the 
various  series  of  hydrocarbons  (and  their  isomeres)  we  have  homologous  series 
of  alcohols.  The  isomeric  alcohols  also  show  properties  different  from  one 
another,  and  yield  different  decomposition  products.  The  isomeric  alcohols  are 
distinguished  as  normal  or  primary,  secondary  and  tertiary  alcohols  ;  a  normal 
alcohol  is  derived  from  a  -normal  paraffin,  and  contains  hydroxyl  in  the  place 
of  a  hydrogen  atom  in  a  methyl  group,  the  constitution  of  normal  ethyl 

CH2.OH 
alcohol  being,  for  instance,  represented  by  the  formula  I 

CH3. 

If  hydroxyl  replaces  but  one  atom  of  hydrogen  in  a  hydrocarbon, 
the  alcohol  is  termed  monatomic ;  diatomic  and  triatomic  alcohols  are 
formed  by  replacement  of  two  or  three  hydrogen  atoms  respectively. 
(Diatomic  alcohols  are  also  termed  glycols.)  As  an  instance  of  a 
diatomic  alcohol  may  be  mentioned  ethylene  alcohol,  C2H4(OH)2, 
while  glycerin,  C3H5(OH)3,  is  a  triatomic  alcohol. 

QUESTIONS. — 391.  How  do  hydrocarbons  occur  in  nature,  and  by  what  pro- 
cesses are  they  formed  in  nature  or  artificially?  392.  State  the  general  physical 
and  chemical  properties  of  hydrocarbons.  393.  What  is  the  general  composi- 
tion of  the  paraffins  ?  394.  State  the  composition  and  properties  of  methane, 
and  also  the  conditions  under  which  it  is  formed  in  nature.  395.  What  is  coal, 
what  are  its  constituents,  from  what  is  it  derived,  and  by  what  process  has  it 
been  formed?  396.  What  is  crude  coal-oil,  what  is  petroleum  ether,  and  what 
is  petrolatum  ?  397.  How  is  illuminating  gas  manufactured,  and  what  are  its 
chief  constituents  ?  398.  Mention  some  of  the  important  substances  found  in 
coal-tar.  399.  Explain  a  method  by  which  the  flashing-point  of  coal-oil  can 
be  determined.  400.  Which  substances  are  termed  volatile  oils,  and  what  are 
their  properties? 


308  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Alcohols  correspond  in  their  composition  to  the  hydroxides  of 
inorganic  substances  ;  both  classes  of  compounds  containing  hydroxyl, 
OH,  which,  in  the  case  of  alcohols,  is  in  combination  with  residues 
containing  carbon  and  hydrogen,  in  the  case  of  inorganic  hydroxides 
with  metals,  as,  for  instance,  in  potassium  hydroxide,  KOH. 

If  we  represent  any  unsaturated  hydrocarbon  by  ALE.  (alcohol 
radical),  the  general  formula  of  the  alcohols  will  be  : 

Monatomic  alcohol.  Diatomic  alcohol.  Triatomic  alcohol. 


/OTT 

Al.Ki-OH  ALBtt<7  Al.Eiii—  OH 

\OH 
or 

ALKiOH  m    Al.Eii(OH)2  ALEUl(OH), 

corresponding  to 

KOH  Caii(OH)2  Bim(OH)3. 

Occurrence  in  nature.  Alcohols  are  not  found  in  nature  in  a  free 
or  uncornbined  state,  but  generally  in  combination  with  acids  as  com- 
pound ethers.  Some  plants,  for  instance,  contain  compound  ethers 
mixed  with  volatile  oils.  The  triatomic  alcohol  glycerin  is  a  normal 
constituent  of  all  fats  or  fatty  oils,  and  is  therefore  found  in  many 
plants  and  in  most  animals. 

Formation  of  alcohols.  Alcohols  are  often  produced  by  fermen- 
tation (ethyl  alcohol  from  sugar),  sometimes  by  destructive  distillation 
(methyl  alcohol  from  w^ood)  :  they  are  obtained  from  compound  ethers 
(which  are  compounds  of  acids  and  alcohols)  by  treating  them  with 
the  alkali  hydroxides,  when  the  acid  enters  into  combination  with 
the  alkali,  whilst  the  alcohols  are  liberated  according  to  the  general 
formula  : 

lc.!>  +  KOH  =  Acl>°  +  A1-E-OH- 

Alcohols  may  be  obtained  artificially  by  various  processes,  as,  for 
instance,  by  treating  hydrocarbons  with  chlorine,  when  the  chloride 
of  a  hydrocarbon  residue  is  formed,  which  may  be  decomposed  by 
alkali  hydroxides  in  order  to  replace  the  chlorine  by  hydroxyl,  when 
an  alcohol  is  formed.  For  instance  : 

C2H6  ^2C1    =      C2H5C1  "  +      HC1. 
Ethane.  Ethyl  chloride. 

C2H5C1     +     KOH   •=•    KC1     -f     C2H5OH, 

Ethyl  Potassium      Potassium  Ethyl 

chloride.          hydroxide.       chloride.  alcohol. 

Properties  of  alcohols.  Alcohols  are  generally  colorless,  neutral 
liquids  ;  some  of  the  higher  members  are  solids,  none  is  gaseous  at 


ALCOHOLS. 


309 


the  ordinary  temperature.  Most  alcohols  are  specifically  lighter  than 
water  ;  the  lower  members  are  soluble  in  or  mix  with  water  in  all 
proportions  ;  the  higher  members  are  less  soluble,  and,  finally,  insolu- 
ble. Most  alcohols  are  volatile  without  decomposition  ;  some  of  the 
highest  members,  however,  decompose  before  being  volatilized. 

Although  alcohols  are  neutral  substances,  it  is  possible  to  replace 
the  hydrogen  of  the  hydroxyl  by  metals,  as,  for  instance,  CH3OH  = 
methyl  alcohol  ;  CH3ONa  =  sodium  methyl  oxide  or  sodium  me- 
thylate. 

The  oxygen  of  alcohols  may  be  replaced  by  sulphur,  when  com- 
pounds are  formed  known  as  hydrosulphides  or  mercaptans;  these 
bodies  may  .be  obtained  by  treating  the  chlorides  of  hydrocarbon 
residues  with  potassium  sulphydrate  : 

C2H5C1    +     KSH    =    KC1    +     C2H5SH. 

By  replacement  of  the  hydrogen  of  the  hydroxyl  in  alcohols  by 
alcohol  radicals  ethers  are  formed  ;  by  replacing  the  same  hydrogen 
with  acid  radicals  compound  ethers  are  produced. 

Monatomic   normal    alcohols   of    the    general   composition 


CnH2 


or  CnH2n 


B.  P. 

Methyl  alcohol      C  H3  OH 

67°  C. 

Ethyl         "            C2H5OH 

78 

Propyl        "            C3H7OH 

97 

Butyl 

C4H9OH 

115 

Amyl 

C5HUOH 

132 

Hexyl 

'           .        .        .                 .     C6  HnOH 

150 

Heptyl 

1                                                 C,  H,-OH 

168 

Octyl 

C8H17OH 

186 

Nonyl          '            C9H19OH 

204 

Cetyl           "            CKH33OH 
Ceryl          «            C27H55OH 
Melissyl     "            C30H61OH 

5(h  , 

79  1   Fusmg- 
85  j     Point. 

Methyl  alcohol,  CH3OH  (Methyl  hydroxide,  Methyl  alcohol,  Wood- 
spirit,  Wood-naphta).  Methyl  alcohol  is  one  of  the  many  products 
obtained  by  the  destructive  distillation  of  wood.  When  pure  it  is  a 
thin,  colorless  liquid,  similar  in  smell  and  taste  to  ethyl  alcohol ;  crude 
wood-spirit,  which  contains  many  impurities,  has  an  offensive  odor 
and  a  nauseous,  burning  taste.  Methyl  alcohol  mixes  in  all  propor- 
tions with  water;  it  dissolves  resins  and  volatile  oils  as  freely  as  ethyl 
alcohol,  and  is  often  substituted  for  the  latter  for  various  purposes  in 
the  arts  and  manufactures. 


310  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Ethyl  alcohol,  C2H5OH  =  46  (Common  alcohol.  Ethyl  hydroxide, 
Spirit),  may  be  obtained  from  ethene,  C2H4,  by  addition  of  the 
elements  of  water,  which  may  be  accomplished  by  agitating  ethene 
with  strong  sulphuric  acid,  when  direct  combination  takes  place  and 
ethyl  sulphuric  acid  is  formed  : 


+        H2SO4  C2H5HSO4. 

Ethene.  Sulphuric  acid.        Ethyl  sulphuric  acid. 

Ethyl  sulphuric  acid  mixed  with  water  and  distilled  yields  sul- 
phuric acid  and  ethyl  alcohol  : 

C2H5HS04    +     H20    =    H2S04    +     C2H5OH. 

Ethyl  alcohol  may  also  be  obtained,  as  already  mentioned,  by  treat- 
ing ethyl  chloride  with  potassium  hydroxide  : 

C2H5C1    +    KOH  KC1    -f     C2H5OH. 

While  the  above  methods  for  obtaining  alcohol  are  of  scientific 
interest,  there  is  but  one  mode  of  manufacturing  it  on  a  large  scale, 
namely,  by  the  fermentation  of  certain  kinds  of  sugar,  especially 
grape-sugar  or  glucose,  C6H12O6.  A  diluted  solution  of  grape-sugar 
under  the  influence  of  certain  ferments  (yeast)  suffers  decomposition, 
yielding  carbon  dioxide  and  alcohol  : 

C6H12O6    :   :    2CO2     -f-     2C2H5OH. 
Glucose.  Carbon  Ethyl 

dioxide.  alcohol. 

Experiment  43.  To  a  solution  of  25  grammes  of  commercial  glucose  (grape- 
sugar)  in  1000  c.c.  of  water,  add  a  little  brewer's  yeast  and  introduce  this  mix- 
ture into  a  flask.  Attach  to  the  flask,  by  means  of  a  perforated  cork,  a  bent 
glass  tube  leading  into  clear  lime-water,  contained  in  a  small  flask.  After 
standing  (a  warm  place  should  be  selected  in  winter  for  this  operation)  a  few 
hours  fermentation  will  commence,  which  can  be  noticed  by  the  evolution  of 
carbon  dioxide,  which,  in  passing  through  the  lime-water,  causes  the  precipi- 
tation of  calcium  carbonate. 

After  fermentation  ceases  connect  the  flask  with  a  condenser  and  distil  over 
50  to  100  c.c.  of  the  liquid.  Verify  in  the  distilled  portion  the  presence  of 
alcohol  by  applying  the  tests  mentioned  below.  For  condensation  of  the  dis- 
tilling vapors  a  Liebig's  condenser,  represented  in  Fig.  40,  may  be  used.  This 
apparatus  consists  of  a  wide  glass  tube  through  which  passes  the  narrow  con- 
densing tube,  connected  with  the  boiling-flask  a.  A  constant  current  of  cold 
water  is  obtained  by  allowing  water  to  flow  into  b,  and  to  escape  by  c.  A  small 
flask  is  placed  under  d  for  collecting  the  distillate. 

By  distilling  the  fermented  liquid  an  alcohol  is  obtained  containing 
large  quantities  of  water;  on  distilling  this  dilute  alcohol  a  second 
and  a  third  time,  collecting  the  first  portions  of  the  distilled  liquid 
separately,  an  alcohol  is  obtained  containing  but  little  water.  These 


ALCOHOLS.  311 


last  quantities  of  water,  amounting  to  about  14  per  cent.,  cannot  U 
removed  by  simple  distillation,  but  may  be  separated  by  mixing  the 
alcohol  with  half  its  weight  of  calcium  oxide,  which  combines  with 
the  water  to  form  calcium  hydroxide,  from  which  the  alcohol  may 
now  be  separated  by  distillation. 


FIG.  40. 


Cf> 


Liebig's  condenser  with  distilling-flask. 

The  alcohol  thus  obtained,  and  containing  not  more  than  1  per 
cent,  of  water,  is  known  as  pure,  absolute,  or  real  alcohol.  The 
alcohol  of  the  U.  8.  P.  contains  91  per  cent,  by  weight,  or  94  per 
cent,  by  volume  of  real  alcohol,  and  has  a  specific  gravity  of  0.820 
at  15°  C.  (59°  F.).  The  diluted  alcohol  is  made  by  mixing  equal 
volumes  of  water  and  alcohol,  and  has  a  specific  gravity  of  0.936;  it 
is  identical  with  the  proof-spirit  of  the  U.  S.  Custom-house  and 
Internal  Revenue  service. 

Pure  alcohol  is  a  transparent,  colorless,  mobile,  and  volatile  liquid, 
of  a  characteristic  rather  agreeable  odor,  and  a  burning  taste ;  it  boils 
at  78°  C.  (172°  F.),  has  a  specific  gravity  of  0.797,  is  of  a  neutral 
reaction,  becomes  syrupy  at — 110°  C.  ( — 166°  F.),  and  solidifies  at 
—130°  C.  (—202°  F.);  it  burns  with  a  non-luminous  flame;  when 
mixed  with  water  a  contraction  of  volume  occurs,  and  heat  is  liber- 
ated ;  the  attraction  of  alcohol  for  water  is  so  great  that  strong 
alcohol  absorbs  moisture  from  the  air  or  abstracts  it  from  membranes, 
tissues,  and  other  similar  substances  immersed  in  it ;  to  this  property 
are  due  its  coagulating  action  on  albumin  and  its  preservative  action 


312  CONSIDERATION  OF  CARBON  COMPOUNDS 

on  animal  substances.  The  solvent  powers  of  alcohol  are  very  exten- 
sive, both  for  inorganic  and  organic  substances ;  of  the  latter  it  readily 
dissolves  essential  oils,  resins,  alkaloids,  and  many  other  bodies,  for 
which  reason  it  is  used  in  the  manufacture  of  the  numerous  official 
tinctures,  extracts,  and  fluid  extracts. 

Alcohol  taken  internally  in  a  dilute  form  has  intoxicating  proper- 
ties ;  pure  alcohol  acts  poisonously ;  it  lowers  the  temperature  of  the 
body  from  0.5°  to  2°  C.  (0.9°  to  3.6°  F.),  although  the  sensation  of 
warmth  is  experienced. 

Analytical  reactions  for  ethyl  alcohol. 

1.  Dissolve  a  small  crystal  of  iodine  in  about  2  cc.  of  alcohol; 
add  to  the  cold  solution  potassium  hydroxide  until  the  brown  color 
of  the  solution  disappears ;  a  yellow  precipitate  of  iodoform,  CHI3, 
forms.     Many  other  alcohols,  aldehyde,  acetone,  etc.,  show  the  same 
reaction. 

2.  Add  to  about  1  c.c.  of  alcohol  the  same  volume  of  sulphuric 
acid ;  heat  to  boiling  and  add  gradually  a  little  more  alcohol :  the 
odor  of  ethyl  ether  will  be  noticed  distinctly  on  further  heating. 

3.  Add  to  a  mixture  of  equal  volumes  of  alcohol  and  sulphuric 
acid,  a  crystal  (or  strong  solution)  of  sodium  acetate :  acetic  ether  is 
formed  and  recognized  by  its  odor. 

4.  To  about  2  c.c.  of  potassium  dichromate  solution  add  0.5  c.c.  of 
sulphuric  acid  and  1  c  c.  of  alcohol :  upon  heating  gently  the  liquid 
becomes  green  from  the  formation  of  chromic  sulphate,  while  alde- 
hyde is  formed  and  may  be  recognized  by  its  odor. 

Alcoholic  liquors.  Numerous  substances  containing  sugar  or  starch  (which 
may  be  converted  into  sugar)  are  used  in  the  manufacture  of  the  various  alco- 
holic liquors,  all  of  which  contain  more  or  less  of  ethyl  alcohol,  besides  color- 
ing matter,  ethers,  compound  ethers,  and  many  other  substances. 

White  and  red  wines  are  obtained  by  the  fermentation  of  the  grape-juice ;  the 
so-called  light  wines  contain  from  10  to  12,  the  strong  wines,  such  as  port  and 
sherry,  from  19  to  25  per  cent,  of  alcohol ;  if  the  grapes  contain  much  sugar, 
only  a  portion  of  it  is  converted  into  alcohol,  whilst  another  portion  is  left 
undecomposed ;  such  wines  are  known  as  sweet  wines.  Effervescent  wines,  as 
champagne,  are  bottled  before  the  fermentation  is  complete ;  the  carbonic  acid 
is  disengaged  under  pressure  and  retained  in  solution  in  the  liquid. 

Beer  is  prepared  by  fermentation  of  germinated  grain  (generally  barley)  to 
which  much  water  and  some  hops  have  been  added;  the  active  principle  of 
hops  is  lupulin,  which  confers  on  the  beer  a  pleasant,  bitter  flavor,  and  the 
property  of  keeping  without  injury.  Light  beers  have  from  2  to  4,  strong  beers, 
as  porter  or  stout,  from  4  to  6  per  cent,  of  alcohol. 


ALCOHOLS.  313 

Spirits  differ  from  either  wines  or  beers  in  so  far  as  the  latter  are  not  dis- 
tilled, and  therefore  contain  also  non-volatile  organic  and  inorganic  substances, 
such  as  salts,  etc.,  not  found  in  the  spirits,  which  are  distilled  liquids  contain- 
ing volatile  compounds  only.  Moreover,  the  quantity  of  alcohol  in  spirits  is 
very  much  larger,  and  varies  from  45  to  55  per  cent.  Of  distilled  spirits  may 
be  mentioned :  American  whiskey,  made  from  fermented  rye  or  Indian  corn ; 
Irish  whiskey,  from  potatoes;  Scotch  whiskey,  from  barley;  brandy  or  cognac,  by 
distilling  French  wines ;  rum.,  by  fermenting  and  distilling  molasses ;  arrack, 
from  fermented  rice ;  gin,  from  various  grains  flavored  with  juniper  berries. 

Amyl  alcohol,  C5HnOH.  This  alcohol  is  frequently  formed  in  small  quanti- 
ties during  the  fermentation  of  corn,  potatoes,  and  other  substances.  When 
the  alcoholic  liquors  are  distilled,  amyl  alcohol  passes  over  toward  the  end  of 
the  distillation,  generally  accompanied  by  propyl,  butyl,  and  other  alcohols, 
and  by  certain  ethers  and  compound  ethers.  A  mixture  of  these  substances 
is  known  as  fusel  oil,  and,  from  this  liquid,  amyl  alcohol  may  be  obtained  in  a 
pure  state.  It  is  an  oily,  colorless  liquid,  having  a  peculiar  odor,  and  a  burning, 
acrid  taste;  it  is  soluble  in  alcohol,  but  not  in  water.  By  oxidation  of  amyl 
alcohol,  valerianic  acid  is  obtained. 

Amylene  hydrate,  Ethyl-dimethyl-carbinol,  C5ffl20,  is  an  alcohol  isomeric  with 
the  above  amyl  alcohol,  but  yielding  only  acetic  acid  on  oxidation.  It  is 
a  colorless  liquid,  having  a  pungent,  ethereal  odor,  and  a  boiling-point  of 
100°  C.  (212°  F.). 

Glycerin,  Glycerinum,  C3H5(OH)3  (Glycerol).  Glycerin  is  the 
triatoinic  or  tri-acid  alcohol  of  the  residue  glyceryl,  C3H5,  formed  by 
removal  of  the  three  atoms  of  hydrogen  from  the  saturated  hydro- 
carbon propane,  C3H8,  and  by  combination  of  the  residue  with  3OEL 

Glycerin  is  a  normal  constituent  of  all  fats,  which  are  glycerin  in 
which  the  three  atoms  of  hydrogen  of  the  hydroxyl  have  been  re- 
placed by  radicals  of  fat  acids.  When  fats  are  treated  with  alkalies^ 
these  latter  combine  with  the  fat  acids,  whilst  glycerin  is  liberated. 
Upon  this  decomposition,  carried  out  on  a  large  scale  in  the  manu- 
facture of  soap,  depends  the  mode  of  obtaining  glycerin. 

Pure  glycerin  is  a  clear,  colorless,  odorless  liquid  of  a  syrupy  con- 
sistence, oily  to  the  touch,  hygroscopic,  very  sweet,  and  neutral  in  re- 
action, soluble  in  water  and  alcohol  in  all  proportions,  but  insoluble  in 
ether,  chloroform,  benzol,  and  fixed  oils ;  its  specific  gravity  is  1.255  ; 
it  cannot  be  distilled  by  itself  without  decomposition,  but  is  volatil- 
ized in  the  presence  of  water,  or  when  hot  steam  is  allowed  to  pass 
through  it. 

Glycerin  is  a  good  solvent  for  a  large  number  of  organic  and  inor- 
ganic substances;  the  solutions  thereby  obtained  are  often  termed 
glycerites ;  official  are  the  glycerites  of  starch,  carbolic  acid,  tannic 
acid,  and  a  few  others. 


314  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Boroglycerin  is  made  by  heating  a  mixture  of  boric  acid  and  gly- 
cerin, when  the  compound  C3H5BO3  is  obtained. 

Analytical  reactions. 

1.  A  borax  bead    immersed  for  a  few  minutes  in  a  solution  of 
glycerin  (made  slightly  alkaline  with  potassium  hydroxide)  imparts 
a  green  color  to  a  non-luminous  flame,  owing  to  the  liberation  of 
boric  acid. 

2.  Glycerin  slightly  warmed  with  an  equal  volume  of  sulphuric 
acid  should  not  turn  dark,  but,  on  further  heating,  the  characteristic, 
irritating  odor  of  acrole'in  is  noticed. 

3.  Fehling's  solution  (see  index)  should  not  cause  a  red  precipita- 
tion on  heating,  indicating  the  absence  of  glucose  and  dextrin. 


Nitre-glycerin,  C3HJNO3)3  ((?^cen/£  £n'-m£rafe,  Glonoin).  When 
glycerin  is  treated  with  nitric  acid,  or,  better,  with  a  mixture  of  con- 
centrated sulphuric  and  nitric  acids,  chemical  action  takes  place 
resulting  in  the  formation  of  glyceryl  mono-nitrate,  or  tri  nitrate, 
substances  belonging  to  the  group  of  compound  ethers,  the  constitu- 
tion of  which  will  be  explained  later. 

C3H5(OH)3  +  3HN03  =  C3H5(N03)3  +  3H2O. 

The  tri-nitro-glycerin  is  the  common  nitro-glycerin,  a  pale-yellow 
oily  liquid,  which  is  nearly  insoluble  in  water,  soluble  in  alcohol, 
crystallizes  at  —  20°  C.  (  —  4°  F.)  in  long  needles,  and  explodes  very 
violently  by  concussion  ;  it  may  be  burned  in  an  open  vessel,  but 
explodes  when  heated  over  250°  C.  (482°  F.). 

Spirit  of  glonoin  is  an  alcoholic  solution  of  nitro-glycerin,  con- 
taining of  this  substance  1  per  cent. 

Dynamite  is  infusorial  earth  impregnated  with  nitro-glycerin. 

Phenols.  The  substances  termed  phenols  are  formed  by  replacement  of 
hydrogen  by  hydroxyl  in  the  aromatic  hydrocarbons  of  the  benzene  series  ; 
they  have  the  constitution  of  alcohols,  but  are  not  alcohols  in  the  sense  in 
which  this  term  is  used.  The  more  important  substances  belonging  to  this 
group  will  be  considered  later. 

QUESTIONS.  —  401.  What  is  the  general  constitution  of  alcohols,  and  what  is 
the  difference  between  monatomic,  diatomic,  and  triatomic  alcohols?  402.  How 
do  alcohols  occur  in  nature?  403.  By  what  processes  may  alcohols  be  formed 
artificially,  and  how  may  they  be  separated  from  their  combinations?  404. 
State  the  general  properties  of  alcohols.  405.  Mention  names  and  composition 
of  the  first  five  members  of  alcohols  of  the  general  composition  Cn  Ebn  4-iOH. 


ALDEHYDES.    HALOID  DERIVATIVES.  315 


42.    ALDEHYDES.     HALOID  DEKIVATIVES. 

Aldehydes.  The  name  aldehyde  is  derived  from  alcohol  dehydro- 
genatum,  referring  to  its  method  of  formation,  viz.,  by  the  removal 
of  hydrogen  from  alcohols,  as,  for  instance : 

C2H6O    —    2H       :    C2H40. 
Ethyl  alcohol.  Acetic  aldehyde. 

This  removal  of  hydrogen  may  be  accomplished  by  various  methods, 
as,  for  instance,  by  oxidation  of  alcohols,  when  one  atom  of  oxygen 
combines  with  two  atoms  of  hydrogen,  forming  water,  whilst  an  alde- 
hyde is  formed  at  the  same  time.  Aldehydes,  when  further  oxidized, 
are  converted  into  acids  ;  aldehydes  are,  consequently,  the  interme- 
diate products  between  alcohols  and  acids,  and  are  frequently  looked 
upon  as  the  hydrides  of  the  acid  radicals.  The  constitution  of  acetic 
acid  may  be  represented  by  the  formula  CH3.CO.OH ;  the  radical  of 
acetic  acid  or  acetyl  is  the  group  CH3.CO,  and  the  hydride  of  acetyl 
is  acetic  aldehyde,  CH3.COH.  It  is  the  group  COH  which  is  char- 
acteristic of,  and  found  in,  all  aldehydes.  Only  a  few  aldehydes  are 
of  practical  interest,  as,  for  instance,  acetic  aldehyde,  paraldchyde,  and 
benzoic  aldehyde,  which  latter  substance  will  be  more  fully  considered 
in  connection  with  the  aromatic  substances. 

Acetic  aldehyde,  C2H4O  or  CH3COH.    Alcohol  may  be  converted 
into  aldehyde  by  the  action  of  various  oxidizing  agents ;   the  one 
generally  used  is  potassium  dichromate,  which  oxidizes  two  hydrogen 
atoms  of  the  alcohol  molecule,  converting  it  into  aldehyde  : 
C2H6O    +    O    =  :    C2H4O    +    H20. 

Experiment  44.  Place  in  a  500  c.c.  flask,  provided  with  a  funnel-tube  and 
connected  with  a  Liebig's  condenser,  6  grammes  of  potassium  dichromate. 
Pour  upon  this  salt  through  the  funnel-tube,  very  slowly,  a  previously  pre- 
pared and  cooled  mixture  of  5  c.c.  of  sulphuric  acid,  24  c  c.  of  water  and  6  c.c. 
of  alcohol.  Chemical  action  begins  generally  without  application  of  heat,  and 
often  becomes  so  violent  that  the  liquid  boils  up,  for  which  reason  a  large  flask 
is  used.  The  escaping  vapors,  which  are  a  mixture  of  aldehyde,  alcohol,  and 
water,  are  collected  in  a  receiver  kept  cold  by  ice.  From  this  mixture  pure 

406.  By  what  process  is  methyl  alcohol  obtained,  under  what  other  names  is  it 
known,  and  what  are  its  properties  ?  407.  Describe  the  manufacture  of  pure 
alcohol  from  sugar.  408.  Give  the  alcoholic  strength  of  the  alcohol  and  diluted 
alcohol  of  the  U.  S.  P.,  and  also  of  spirit  of  wine,  proof-spirit,  light  wines,  heavy 
wines,  beers,  and  spirits.  409.  What  are  the  general  properties  of  common 
alcohol?  410.  What  is  glycerin,  how  is  it  found  in  nature,  how  is  it  obtained, 
and  what  are  its  properties? 


316  CONSIDERATION  OF  CARSON  COMPOUNDS. 

aldehyde  may  be  obtained  by  repeated  distillation.  Use  the  distillate  for 
silvering  a  test-tube  by  adding  some  ammoniated  silver  nitrate.  How  much 
potassium  dichromate  is  needed  for  the  conversion  of  5  grammes  of  pure 
alcohol  into  aldehyde? 

Aldehyde  is  a  neutral,  colorless  liquid,  having  a  strong  and  charac- 
teristic odor ;  it  mixes  with  water  and  alcohol  in  all  proportions  and 
boils  at  21°  C.  (69.8°  F.).  The  most  characteristic  chemical  property 
of  aldehyde  is  its  tendency  to  combine  directly  with  a  great  number 
of  substances;  thus  it  combines  with  hydrogen  to  form  alcohol,  with 
oxygen  to  form  acetic  acid,  with  ammonia  to  form  aldehyde-ammonia, 
C2H4O.NH3,  a  beautifully  crystallizing  substance,  with  hydrocyanic 
acid  to  form  aldehyde  hydrocyanide,  C2H4O.HCN,  and  with  many 
other  substances.  In  the  absence  of  such  other  substance  it  unites 
often  with  itself,  forming  polymeric  modifications,  such  as  paralde- 
hyde  and  metaldehyde. 

Aldehyde  is  a  strong  reducing  agent,  which  property  is  used  in  the 
silvering  of  glass,  which  is  done  by  adding  aldehyde  to  an  ammoniacal 
solution  of  silver  nitrate,  when  metallic  silver  is  deposited  on  the  walls 
of  the  vessel  or  upon  substances  immersed  in  the  solution. 

Paraldehyde,  C6H12O3.  When  a  few  drops  of  concentrated  sul- 
phuric acid  are  added  to  aldehyde,  this  becomes  hot  and  solidifies  on 
cooling  to  0°  C.  (32°  F.).  This  solid  crystalline  mass  of  paralde- 
hyde,  which  liquefies  at  10.5°  C.  (51°  F.),  has  been  formed  by  the 
direct  union  of  three  molecules  of  common  aldehyde.  Paraldehyde 
is  soluble  in  8.5  parts  of  water,  boils  at  124°  C.  (253°  F.),  and  is 
reconverted  into  common  aldehyde  by  boiling  it  with  dilute  sulphuric 
or  hydrochloric  acid. 

Metaldehyde,  (C2H4O)z,  is  another  polymeric  modification  of  aldehyde,  ob- 
tained by  a  process  similar  to  the  one  mentioned  for  paraldehyde,  but  at  a 
lower  temperature.  It  is  a  solid  crystalline  substance,  insoluble  in  water,  but 
slightly  soluble  in  alcohol,  ether,  and  chloroform. 

Trichloraldehyde,  Chloral,  C2HC13O  or  CC13.COH  (Trichloracetyl 
hydride).  This  substance  may  be  looked  upon  as  acetic  aldehyde, 
C2H4O,  in  which  three  atoms  of  hydrogen  have  been  replaced  by 
chlorine.  It  is  made  by  passing  a  rapid  stream  of  dry  chlorine  into 
pure  alcohol  to  saturation,  keeping  the  alcohol  cool  during  the  first 
few  hours,  and  warming  it  gradually  until  the  boiling-point  is 
reached.  According  to  the  quantity  of  alcohol  operated  on,  the  con- 
version requires  several  hours  or  even  days.  The  crude  liquid  pro- 


ALDEHYDES.    HALOID  DERIVATIVES.  317 

duct  separates  into  two  layers ;  the  lower  is  removed  and  shaken  with 
three  times  its  volume  of  strong  sulphuric  acid  and  distilled,  the  dis- 
tillate is  mixed  with  calcium  oxide  and  again  distilled ;  the  portion 
passing  over  between  94°  and  99°  C.  (201°  and  210°  F.)  is  collected. 
The  decomposition  taking  place  between  alcohol  and  chlorine  may 
be  explained  by  the  formation  of  aldehyde  : 

C2H60     +    2C1    =    C2H40     +    2HC1, 

and  by  the  subsequent  replacement  of  hydrogen  by  chlorine : 
C2H4O     -f     6C1    =    C2HC130     -f    3HC1 

The  actual  decomposition  is,  however,  somewhat  more  complicated, 
numerous  other  products  being  formed  at  the  same  time.  By  treat- 
ment with  sulphuric  acid  these  other  substances  are  removed. 

Chloral  is  a  colorless,  oily  liquid,  having  a  penetrating  odor  and  an 
acrid,  caustic  taste;  its  specific  gravity  is  1.5,  and  its  B.  P.  95°  C. 
(202°  F.). 

Chloral  hydrate,  Chloral,  U.  S.  P.,  C2HC13O.H2O=165.2.  When 
water  is  added  to  chloral  the  two  substances  combine,  heat  is  dis- 
engaged, and  the  hydrate  of  chloral  is  formed,  which  is  a  crystalline, 
colorless  substance,  having  an  aromatic,  penetrating  odor,  a  bitter, 
caustic  taste,  and  a  neutral  reaction  ;  it  is  freely  soluble  in  water, 
alcohol,  and  ether,  also  soluble  in  chloroform,  carbon  disulphide, 
benzene,  fatty  and  essential  oils,  etc. ;  it  liquefies  when  mixed  with 
carbolic  acid  or  with  camphor;  it  melts  at  58°  C.(136°  F.),  and  boils 
at  95°  C.  (203°  F.),  and  also  volatilizes  slowly  at  ordinary  temperature. 

Chloral,  and  its  hydrate,  are  decomposed  by  weak  alkalies  into 
chloroform  and  a  formate  of  the  alkali  metal : 

C2HC130     +     KHO  KCHO2     +     CHC13. 

Chloral.  Potassium         Potassium          Chloroform, 

hydroxide.  formate. 

This  decomposition  was  believed  to  take  place  in  the  animal  body,  and 
especially  in  the  blood,  whenever  chloral  was  given  internally,  but  recent  in- 
vestigations seem  to  contradict  this  assumption.  There  is  no  chemical  antidote 
which  may  be  used  in  cases  of  poisoning  by  chloral,  and  the  treatment  is, 
therefore,  confined  to  the  use  of  the  stomach-pump  and  to  the  maintenance  of 
respiration. 

Analytical  reactions  for  chloral. 

1.  Chloral  or  chloral  hydrate  heated  with  potassium  hydroxide  is 
converted  into  potassium  formate  and  chloroform,  which  latter  may 
be  recognized  by  its  odor.  (See  explanation  above.) 


318  CONSIDERATION  OF  CARBON  COMPOUNDS. 

2.  Heated  with  silver  nitrate  and  ammonium  hydroxide  a  silver- 
mirror  is  formed  on  the  glass. 

3.  Heated  with  Fehling's  solution  a  red  precipitate  is  formed. 
See  also  reactions  2  and  6  for  chloroform  below. 

Chloroform,  Chloroformum,  CHC13  =  119.2  (Trichlormeihane, 
Dichlormethyl  chloride).  When  either  chlorine,  bromine,  or  iodine  is 
allowed  to  act  upon  methane,  CH4,  a  number  of  substitution  products 
are  formed.  Thus,  if  methane  is  considered  as  methyl  hydride, 
CH3H,  the  first  product  of  substitution  is  methyl  chloride,  CH3C1 ; 
the  second  is  monochlor methyl  chloride,  CH2C1C1  ;  the  third  is 
dichlormethyl  chloride  or  chloroform,  CHC12C1 ;  and  the  fourth  is 
carbon  tetrachloride,  CC14.  Similar  products  are  formed  by  the 
action  of  iodine  or  bromine  upon  methane,  or,  in  fact,  upon  any  of 
the  paraffins. 

Chloroform  is,  however,  not  obtained  for  commerce  by  the  above 
process,  but  by  the  action  of  bleaching-powder  and  calcium  hydroxide 
on  alcohol.  The  three  substances  named,  after  being  mixed  with  a 
considerable  quantity  of  water,  are  heated  in  a  retort  until  distilla- 
tion commences  ;  the  crude  product  of  distillation  is  an  impure  chloro- 
form, which  is  purified  by  mixing  it  with  strong  sulphuric  acid  and 
allowing  the  mixture  to  stand ;  the  upper  layer  of  chloroform  is 
removed  and  treated  with  sodium  carbonate  (to  remove  any  acids) 
and  distilled  over  calcium  oxide  (to  remove  water). 

The  explanation  of  the  formation  of  chloroform  by  the  above  process  ha* 
indirectly  been  given  in  connection  with  the  consideration  of  chloral,  where  it 
has  been  shown  that  alcohol  is  converted  by  the  action  of  chlorine  first  inta 
aldehyde  and  subsequently  into  chloral,  which,  upon  being  treated  with 
alkalies,  is  decomposed  into  an  alkali  formate  and  chloroform. 

The  action  of  the  chlorine  of  the  calcium  hypochlorite  (which  is  the  active 
principle  in  bleaching-powder)  upon  the  alcohol  is  similar  to  that  of  free 
chlorine  upon  alcohol;  in  both  cases  aldehyde,  and  afterward  chloral,  are 
formed,  which  latter,  in  the  manufacture  of  chloroform,  is  decomposed  by  the 
calcium  hydroxide  into  chloroform  and  calcium  formate.  The  last-named  salt 
is,  however,  not  found  in  the  residue  of  the  distillation,  because  it  is  decomposed 
by  bleaching-powder  and  calcium  hydroxide  into  calcium  carbonate,  chloride, 
and  water : 

Ca(CHO2)2  +  Ca(ClO)2  +  Ca(OH)2  =  2CaCO3  +  CaCl2  +  2H2O. 

If  the  various  intermediate  steps  of  the  decomposition  are  not  considered,  the 
process  may  be  represented  by  the  following  equation  : 

4C2H60  +  8CafC10)2  ==  2CHC13  -f-  3[Ca(CHO2)2]  +  5CaCl2  +  8H2O. 
Alcohol.  Calcium        Chloroform.  Calcium  Calcium         Water, 

hypochlorite.  formate.  chloride. 


ALDEHYDES.    HALOID  DERIVATIVES.  319 

Chloroform  is  now  made  extensively  by  the  action  of  bleaching-powder  upon 
acetone ;  the  reaction  takes  place  thus  : 

2CO(CH3)2  -f-  3Ca(C10)2  =  2CHC13  +  2Ca(OH)2  +  Ca(C2H3O2)2. 
Acetone.  Calcium          Chloroform.          Calcium  Calcium 

hypochlorite.  hydroxide.  acetate. 

Pure  chloroform  is  a  heavy,  colorless  liquid,  of  a  characteristic 
ethereal  odor,  a  burning,  sweet  taste,  and  a  neutral  reaction  ;  it  is  but 
very  sparingly  soluble  in  water,  but  miscible  with  alcohol  and  ether 
in  all  proportions  ;  the  specific  gravity  of  pure  chloroform  is  1.50, 
but  a  small  quantity  of  alcohol  (from  one-half  to  one  per  cent.), 
allowed  to  be  present  by  the  U.  S.  P.,  causes  the  specific  gravity  to 
be  about  1.488;  boiling-point  62°  C.  (143°  F.),  but  rapid  evapora- 
tion takes  place  at  all  temperatures. 

Chloroform  should  be  tested  for  excess  of  alcohol  by  specific  gravity ;  for 
hydrochloric  acid  and  chlorine  by  shaking  it  with  water,  which  afterward 
should  not  give  a  precipitate  with  silver  nitrate ;  for  aldehyde  by  heating  with 
solution  of  potassium  hydroxide,  which  should  not  be  colored  brown;  for 
empyreumatic  and  other  organic  compounds  by  shaking  with  an  equal  volume 
of  pure  sulphuric  acid,  which  should  remain  colorless;  or  by  evaporation, 
when  no  residue  should  be  left  and  no  odor  should  be  perceptible  after  the 
chloroform  has  been  volatilized. 


Analytical  reactions  for  chloroform. 

1.  Dip  a  strip  of  paper  into  chloroform  and  ignite.     The  flame  has 
a  green  mantle  and  emits  vapors  of  hydrochloric  acid,  rendered  more 
visible  upon  the  approach  of  a  glass  rod  moistened  with  water  of 
ammonia. 

2.  Add  a  drop  of  chloroform  and  a  drop  of  aniline  to  some  alco- 
holic solution  of  potassium  hydroxide  and  heat  gently  :  a  peculiar, 
penetrating,  offensive  odor  of  benzo-isonitril,  C6H5NC,  is  noticed. 
(Chloral  shows  the  same  reaction.) 

3KOH  +  C6H5.NH2  =  C6H5NC  +  3KC1  +  3H2O 


3.  Add  some  chloroform  to    Fehling's   solution  and  heat  :    red 
cuprous  oxide  is  precipitated. 

4.  Vapors  of  chloroform,  when  passed  through  a  glass  tube  heated 
to  redness,  are  decomposed  into  carbon,  chlorine,  and  hydrochloric 
acid.     The  two  latter  should  be  passed  into  water,  and  may  be  recog- 
nized by  their  action  on  silver  nitrate  (white  precipitate  of  silver 
nitrate)  and  on  mucilage  of  starch,  to  which  potassium  iodide  has 
been  added  (blue  iodized  starch  is  formed). 


320  CONSIDERATION  OF  CARBON  COMPOUNDS. 

5.  Heat  some  chloroform  with  solution  of  potassium  hydroxide  and 
a  little  alcohol.     Chloroform  is  decomposed  into  potassium  chloride 
and  formate : 

CHCL,  -f  4KOH  =  3KC1  +  KCHO2  +  2H2O. 

Divide  solution  into  two  portions.  Acidulate  one  portion  with 
nitric  acid,  boil,  and  add  silver  nitrate  :  white  precipitate  of  silver 
nitrate.  To  second  portion  add  a  little  water  of  ammonia  and  a 
crystal  of  silver  nitrate :  a  mirror  of  metallic  silver  will  be  formed 
after  heating  slightly. 

6.  Add  to  1  c.c.  of  chloroform  about  0.3  gramme  of  resorcin  in 
solution,  and  3  drops  of  solution  of  sodium  hydroxide  ;  boil  strongly  : 
a  yellowish-red  color  is  produced,  and  the  liquid  shows  a  beautiful 
yellow-green  fluorescence.     (Chloral  shows  the  same  reaction.) 

In  cases  of  poisoning  chloroform  is  generally  to  be  sought  for  in  the  lungs 
and  blood,  which  are  placed  in  a  flask  connected  with  a  tube  of  difficultly 
fusible  glass.  By  heating  the  flask  the  chloroform  is  expelled  and  decomposed 
in  the  heated  glass  tube,  as  stated  above  in  reaction  4.  Another  portion  of 
chloroform  should  be  distilled  without  decomposing  it,  and  the  distillate  tested 
as  above  stated. 

What  has  been  said  above  regarding  antidotes  to  chloral  holds  good  for 
chloroform  also. 

Bromoform,  CHBr3  ( Dibromomethyl  bromide).  Obtained  by  gradu- 
ally adding  bromine  to  a  cold  solution  of  potassium  hydroxide  in 
methyl  alcohol  until  the  color  is  no  longer  discharged,  and  rectifying 
over  calcium  chloride. 

Bromoform  is  a  colorless  liquid  which  has  an  aromatic  odor  and  a 
sweettaste.  Sp.gr.2.9;  B.  P.  150°C.  (302°  F.)  ;  solidifiesat  — 9°C. 
(158°  F.).  It  is  sparingly  soluble  in  water,  soluble  in  alcohol  and 
ether.  Its  physiological  action  is  similar  to  that  of  chloroform. 

lodoform,  lodoformum,  CHI3  =  292.6  (Diiodomethyl  iodide). 
This  compound  is  analogous  in  its  constitution  to  chloroform  and 
bromoform.  It  is  made  by  heating  together  an  aqueous  solution  of 
an  alkali  carbonate,  iodine,  and  alcohol  until  the  brown  color  of 
iodine  has  disappeared ;  on  cooling,  iodoform  is  deposited  in  yellow 
scales,  which  are  well  washed  with  water  and  dried  between  filtering 
paper.  (For  an  explanation  of  the  chemical  changes  taking  place  see 
above,  under  chloral  and  chloroform.) 

lodoform  occcurs  in  small,  lemon-yellow,  lustrous  crystals,  having 
a  peculiar,  penetrating  odor,  and  an  unpleasant,  sweetish  taste ;  it  is 


ALDEHYDES.    HALOID  DERIVATIVES.  321 

nearly  insoluble  in  water  and  acids,  soluble  in  alcohol,  ether,  fatty 
and  essential  oils.     It  contains  96.7  per  cent,  of  iodine. 

lodoform  digested  with  an  alcoholic  solution  of  potassium  hy- 
droxide imparts,  after  acidulation  with  nitric  acid,  a  blue  color  to 
starch  solution. 

Experiment  45.  Dissolve  4  grammes  of  crystallized  sodium  carbonate  in  6 
c.c.  of  water :  add  to  this  solution  1  c.c.  of  alcohol ;  heat  to  about  70°  C.  (158° 
F.),  and  add  gradually  1  gramme  of  iodine.  A  yellow  crystalline  deposit  of 
iodoform  separates. 

Ethyl  bromide,  C.,H5Br  (Hydrobromic  ether}.  Obtained  by  the  simultaneous 
action  of  phosphorus  and  bromine  on  ethyl  alcohol.  It  is  a  colorless,  ethereal 
liquid,  which  boils  at  40°  C.  (104°  F.)  and  has  a  sp.  gr.  of  1.473. 

Sulphonal,  (CH3)2C(C2H5S02)2,  Dimethyl-diethylsulphonyl-methane.  It  has 
been  stated  before  that  mercaptans  are  alcohols  in  which  the  oxygen  is  replaced 
by  sulphur.  Alcohol  treated  with  oxidizing  agents  are  converted  into  acids  by 
exchanging  two  atoms  of  hydrogen  for  one  atom  of  oxygen.  Mercaptans 
behave  differently ;  they  combine  directly  with  three  atoms  of  oxygen,  forming 
compounds  known  as  sulphonic  adds.  Thus,  ethyl  mercaptan,  C2H5HS,  when 
treated  with  nitric  acid,  is  converted  into  ethyl-sulphonic  acid,  C2H5HSO3. 
The  radical  of  this  acid,  known  as  ethylsulphonyl,  C2H5S02,  may,  by  indirect 
process,  be  caused  to  replace  hydrogen  in  methane,  CH4,  twice,  while  the  two 
remaining  methane  hydrogen  atoms  can  be  replaced  by  methyl.  The  compound 
thus  obtained  is  the  dimethyl-diethylsulphonyl-methane,  or  sulphonal.  The 
relations  between  methane  and  some  of  its  derivatives,  which  have  been  con- 
sidered in  this  chapter,  may  be  shown  graphically  thus  : 

H  Cl  I 

H— C-H  H— C— Cl  H— C— I 

I  I  I 

H    -  Cl  I 

Methane.  Chloroform.  lodoform. 


COH  COH  CH3 

I  I  I 

H— C— H  Cl— C— Cl  CH3— C— C2H5SO2 

H  Cl  C2H5SO2. 

Aldehyde.  Chloral.  Sulphonal. 

Sulphonal  is  a  white  crystalline  substance,  having  neither  odor  nor  taste ;  it 
is  soluble  in  15  parts  of  boiling  and  500  parts  of  cold  water,  soluble  with  diffi- 
culty in  alcohol ;  it  fuses  at  130°  C.  (266°  F.),  and  volatilizes  at  about  300*  C. 
(572°  F.),  with  partial  decomposition.  A  mixture  of  sulphonal  with  either 
wood  charcoal  or  with  potassium  cyanide  evolves,  on  heating,  the  characteristic 
odor  of  mercaptan. 

QUESTIONS. — 411.  What  is  an  aldehyde,  and  what  are  its.  relations  to  alco- 
hols and  acids?  412.  State  the  composition  of  acetic  aldehyde.  413.  Explain 
the  action  of  chlorine  upon  alcohol.  414.  Give  the  composition  and  properties 

21 


322  CONSIDERATION  OF  CARBON  COMPOUNDS. 

43.    MONOBASIC  FATTY  ACIDS. 

General  constitution  of  organic  acids.  When  hydroxyl,  OH, 
replaces  hydrogen  in  hydrocarbons,  alcohols  are  formed ;  when  the 
univalent  group,  CO2H,  known  as  carboxyl,  replaces  hydrogen  in 
hydrocarbons,  acids  are  formed.  Monatomic,  diatomic,  and  triatomic 
alcohols  are  formed  by  introducing  hydroxyl  once,  twice,  or  three 
times  respectively  into  hydrocarbon  molecules;  monobasic,  dibasic, 
and  tribasic  acids  are  formed  by  substituting  one,  two,  or  three 
hydrogen  atoms  by  carboxyl.  For  instance  : 

Hydrocarbons.  Monobasic  acids.  Dibasic  acids. 

/TTT  r^TT    C*C\  TT  C*£T  /t/OjjJti 

^-LL^  ^Aig.  l-AJj-f-  '^'**1\    C*f\   TT* 

Methane.  Acetic  acid.  Malonic  acid. 

/C02H 


C2H6  C2H5  CO2H 

Ethane.  Propionic  acid.  Succinic  acid. 

The  constitution  of  carboxyl  is  represented  by  O=C — O — H, 
which  shows  that  of  the  four  affinities  of  the  carbon  atom,  two  are 
saturated  by  an  atom  of  oxygen,  one  by  hydroxyl,  whilst  one  is 
unprovided  for;  any  univalent  hydrocarbon  residue  may  attach  itself 
to  this  unprovided  affinity,  when  an  acid  is  formed.  Acids  may  be 
looked  upon,  therefore,  as  being  composed  of  hydrocarbon  residues 
and  hydroxyl,  united  by  the  bivalent  radical  CO,  termed  carbonyl. 
By  replacement  of  the  hydrogen  of  the  hydroxyl  (or  of  the  carboxyl, 
which  is  the  same)  by  metals  the  various  salts  are  formed. 

What  is  termed  the  acid  radical  is  the  group  of  the  total  number 
of  atoms  present  in  the  molecule,  with  the  exception  of  the  hydroxyl. 
In  acetic  acid,  C2H4O2,  for  instance,  the  radical  is  CH3CO,  or  C2H3O, 
which  group  of  atoms,  known  as  acetyl,  is  characteristic  of  acetic 
acid,  and  of  all  acetates,  and  may  often  be  transferred  from  one  com- 
pound into  another  without  decomposition. 

The  difference  between  alcohol  radicals  and  acid  radicals  may  also 
be  stated,  by  saying  that  the  first  contain  carbon  and  hydrogen  only, 
while  acid  radicals  contain  carbon,  hydrogen,  and  oxygen. 

of  chloral  and  chloral  hydrate.  415.  What  decomposition  takes  place  when 
alkalies  act  upon  chloral?  416.  Describe  the  process  of  preparing  and  purify- 
ing chloroform.  417.  What  is  the  composition  of  chloroform  and  what  are 
its  properties?  418.  How  is  chloroform  tested  for  impurities?  419.  By  what 
tests  may  chloroform  be  recognized?  420.  How  is  iodoform  made,  and  what 
are  its  properties  ? 


MONOBASIC  FA  TTY  ACIDS.  323 

In  a  similar  manner,  as  there  are  homologous  series  of  alcohols 
corresponding  to  the  various  series  of  hydrocarbons,  there  are  also 
homologous  series  of  organic  acids  running  parallel  with  the  corre- 
sponding series  of  hydrocarbons  or  alcohols. 

Occurrence  in  nature.  Organic  acids  are  found  and  formed  both 
in  vegetables  and  animals,  and  are  present  either  in  the  free  state,  or 
(and  more  generally)  in  combination  with  bases  as  salts,  or  with 
alcohols  as  compound  ethers.  Uncombined  or  as  salts  are  found,  for 
instance,  citric,  tartaric,  and  oxalic  acids  in  plants,  formic  acid  in 
some  insects,  uric  acid  in  urine,  etc.  ;  as  compound  ethers  are  found 
many  of  the  fatty  acids  in  the  various  fats. 

Some  organic  acids  are  also  found  as  products  of  the  decomposition 
of  organic  matters  in  nature. 

Formation  of  acids.  Many  acids  are  produced  by  oxidation  of 
alcohols.  As  intermediate  products  are  formed  aldehydes,  which 
may  be  looked  upon  (as  stated  in  the  last  chapter)  as  alcohols  from 
which  two  atoms  of  hydrogen  have  been  removed.  For  instance: 

C2H5OH    +    O    =    C2H3OH    -f    H2O. 
Ethyl  alcohol.  Acetic  aldehyde. 

C2H3OH    -f    O    =    C2H3O.OH. 
Acetic  aldehyde.  Acetic  acid. 

Acids  are  obtained  from  compound  ethers  by  boiling  them  with 
alkalies,  when  salts  are  formed,  which  may  be  decomposed  by  sul- 
phuric or  other  acids.  For  instance  : 

KOH  =  C2 


Ethyl  acetate.     Potassium      Potassium        Ethyl  alcohol. 
hydroxide.         acetate. 

2C2H3KO8  -f  H2SO4  =  2C2H4O2  -f  K2SO4. 
Potassium        Sulphuric     Acetic  acid.      Potassium 
acetate.  acid.  sulphate. 

Acids  are  formed  also  by  destructive  distillation  (acetic  acid)  ;  by 
fermentation  (lactic  acid)  ,  by  putrefaction  (butyric  acid)  ;  by  oxida- 
tion of  many  organic  substances  (oxalic  acid  by  oxidation  of 
starch),  etc. 

Properties.  Organic  acids  show  the  characteristics  mentioned  of 
inorganic  acids,  viz.,  when  soluble,  have  an  acid  or  sour  taste,  redden 
litmus,  and  contain  hydrogen  replaceable  by  metals,  with  the  forma- 
tion of  salts. 

Most  organic  acids,  and  especially  the  higher  members,  show  these 
acid  properties  in  a  less  marked  degree  than  inorganic  acids  ;  in  fact, 


324 


CONSIDERATION  OF  CARBON  COMPOUNDS. 


they  become  so  weak  that  the  acid  properties  can  often  scarcely  be 
recognized.  As  stated  above,  mono-,  di-,  and  tri-basic  organic  acids 
are  known,  the  latter  two  being  capable  of  forming  normal,  acid,  or 
double  salts. 

Most  organic  acids  are  colorless,  some  of  the  lower  and  volatile 
acids  have  a  characteristic  odor,  but  most  of  them  are  odorless  ;  most 
organic  acids  are  solids,  some  liquids,  scarcely  any  gaseous  at  the  ordi- 
nary temperature.  Any  salt  formed  by  the  union  of  an  organic  acid 
and  a  non- volatile  metal  (especially  alkali  metal)  leaves  the  carbonate 
of  this  metal  after  the  salt  has  suffered  combustion.  It  is  for  this 
reason  that  ashes  contain  metals  largely  in  the  form  of  carbonates. 

Whilst  the  hydrogen  of  the  hydroxyl  may  be  replaced  by  metals 
or  by  other  residues,  the  hydrogen  of  the  acid  radical  may  often  be 
replaced  by  chlorine,  and  the  oxygen  of  the  hydroxyl  by  sulphur. 
The  acids  formed  by  this  last  reaction  are  known  as  thio  acid*,  for 
instance,  thio-acetic  acid,  C2H4OS. 

When  the  hydrogen  of  the  hydroxyl  is  replaced  by  a  second  acid 
radical  (of  the  same  kind  as  the  one  forming  the  acid)  the  so-called 
anhydrides  are  produced,  which  correspond  to  the  inorganic  anhy- 
drides. For  instance : 


HN03  or  tf02.O 

Nitric  acid. 

N02\0 

N02/° 

Nitric  anhydride. 


C2H402  or  C2H3O.OH. 

Acetic  acid. 

C2H30\0 

C2H30/a 

Acetic  andydride. 


Amido-adds  are  compounds  obtained  from  acids  by  replacement  of 
a  hydrogen  atom  by  NH2 ;  these  compounds  will  be  spoken  of  later 
in  connection  with  amides. 

Patty  acids  of  the  general  composition, 
CnH2nO2  or 


Fusing-    Boiling- 

point. 

point. 

Formic  acid, 

H  C02H 

+  4°C. 

100°C. 

Acetic  acid, 

C  H3C02H 

+17 

118 

Propionic  acid, 

C2  H5  CO2H 

—21 

140 

Butyric  acid, 

C3  H7  C02H 

—20 

162 

Valerianic  acid, 

C4  H9  C02H 

—16 

185 

Caproic  acid, 

C5  HUC02H 

—  2 

205 

CEnanthylic  acid, 

C6  H13C02H 

—10 

224 

Caprylic  acid, 

C7  H15C02H 

+14 

236 

Pelargonic  acid, 

C8  H17C02H 

18 

254 

Capric  acid, 

C9  H19C02H 

30 

270 

Laurie  acid, 

CUH23C02H 

43 

I 

Myristic  acid, 

C13H27C02H 

54 

/ 

Occurs  in : 

Eed  ants  and  some  plants,  etc. 
Vegetable  and  animal  fluids. 
Sweat,  fluids  of  the  stomach,  etc. 
Butter. 

Valerian  root. 
Butter. 
Castor  oil. 

Butter ;  cocoanut  oil. 
Leaves  of  geranium. 
Butter. 

Cocoanut  oil. 


MONOBASIC  FATTY  ACIDS.  325 


Omrstn: 

Palmitic  acid,  C15H31CO2H  62  .....        Palm  oil,  butter. 

Margaric  acid,  C16H33CO2H  60  .....         (Obtained  artificially.) 

Stearic  acid,  C17H35CO2H  70  .....         Most  solid  animal  fats. 

Arachidic  acid,  C19H39CO2H  75  .....  -| 

Behenic  acid,  C21H43CO2H  76  .....  j-     Oils  of  certain  plants. 

Hysenicacid,  C24H49CO2H  77  .....  J 

Ceroticacid,  C26H33CO2H  80  .....  1      Beeswax 

Melissic  acid,  C^H^CO^H.  90  .....  / 

The  name  fatty  acids  has  been  given  to  these  acids  on  account  of 
their  frequent  occurrence  in  fats,  and  also  in  allusion  to  the  some- 
what fatty  appearance  of  the  higher  members  of  the  series. 

The  gradual  change  of  properties  which  the  members  of  an  homol- 
ogous series  show,  is  well  marked  in  the  series  of  fatty  acids,  thus: 

First  member.  Last  member. 

Is  liquid.  Is  solid. 

Volatilized  at  100°  C.  Not  volatilized  without  decomposition. 

Strongly  acid.  Scarcely  acid. 

Strongly  odoriferous.  Odorless. 

Easily  soluble  in  water.  Insoluble  in  water. 

Produces  no  grease  spot.  Produces  a  grease  spot. 
Forms  salts  easily  soluble  without         Forms  salts  which  are  insoluble  or  de- 
decomposition.  composed  by  water. 

The  intermediate  members  of  the  series  show  intermediate  proper- 
ties, and  this  change  in  properties  is  in  proportion  to  the  gradual 
change  in  molecular  weight. 

Formic  acid,  H.CO2H  or  CHO.OH.  This  acid  is  found  in  the 
red  ant  and  in  other  insects,  which  eject  it  when  irritated.  It  is  also 
contained  in  some  plants,  as,  for  instance,  in  the  leaves  of  the  sting- 
ing nettle. 

It  is  formed  by  the  oxidation  of  methyl  alcohol  : 

CH30    +    02    =    CH,02    +    H20, 
Methyl  alcohol.  Formic  acid. 

by  the  action  of  carbonic  oxide  on  potassium  hydroxide  : 

KOH    +    CO    =    KCHO2, 

Potassium  formate. 

by  the  action  of  potassium  hydroxide  on  chloroform  : 
CHC13  4-  4KOH  ==  3KC1  +  2H2O  -f-  KCHO2, 

by  heating  equal  parts  of  glycerin  and  oxalic  acid,  when  the  latter  is 
split  up  into  carbon  dioxide  and  formic  acid,  which  may  be  separated 
from  the  glycerin  by  distillation  : 

C2H204       :    C02    +    CH202. 

Oxalic  acid.  Formic  acid. 


326  CONSIDERATION  OF  CARBON  COMPOUNDS. 

It  is  also  a  product  of  the  decomposition  of  sugar,  starch,  etc. 
Formic  acid  is  a  colorless  liquid  having  a  penetrating  odor,  and  a 
strongly  acid  taste ;  it  produces  blisters  on  the  skin  ;  it  is  a  powerful 
deoxidizer,  being,  when  thus  acting,  converted  into  carbon  dioxide 

and  water : 

CH202    +    O    =    CO2    +    H20. 

Acetic  acid,  H.C2H3O2,  or  C2H3O.OH,  or  CH3.CO2H  —  60. 
The  most  important  alcohol  is  ethyl  alcohol,  and  the  most  largely 
used  organic  acid  is  acetic  acid,  obtained  from  ethyl  alcohol  by  oxi- 
dation. Acetic  acid  is  found  in  combination  with  alkali  metals  in 
the  juices  of  many  plants,  also  in  the  secretions  of  the  glands,  etc. 

Acetic  acid  is  formed  chiefly  either  by  the  oxidation  of  alcohol 
(and  aldehyde)  or  by  the  destructive  distillation  of  wood.  It  is  pi 
duced  commercially  on  a  large  scale  as  follows  :  A  diluted  ale 
(8  to  10  per  cent.)  is  allowed  to  trickle  down  slowrV  through 
shavings  contained  in  high  casks  having  ne^brate^v  sides  in/order  to 
allow  a  free  circulation  of  the  aJfVvthe^.tynpera^eKsVkyt  at  about 
24°  to  30°  C.  (75°  to  86°  F.),  arid 4lk4iqi^NSavin^^d  through 
the  shavings  is  repeatedly  poured  back  in  order  tofcause  complete 
oxidation.  When  the  latter  object  has  been  accomplished  the  liquid 
is  a  diluted  acetic  acid. 

It  appears  that  the  conversion  of  alcohol  into  acetic  acid  is  greatly 
facilitated  by  the  presence  of  a  microscopic  organism  (mycoderma 
aceti)  commonly  termed  "mother  of  vinegar."  This  serves  in  some 
unexplained  way  to  convey  the  atmospheric  oxygen  to  the  alcohol. 
The  term  "  acetic  fermentation  "  is  often  applied  to  this  conversion, 
although  it  is  not  a  true  fermentation,  since  no  splitting  up  of  the 
alcohol  molecule  into  other  less  complex  compounds,  but  a  process  of 
slow  oxidation,  takes  place. 

The  second  process  for  manufacturing  acetic  acid  is  the  heating  of 
wood  to  a  red  heat  in  iron  retorts,  when  numerous  products  (gases, 
aqueous  and  tarry  substances)  are  formed.  The  aqueous  products 
contain,  besides  other  substances,  methyl  alcohol  and  acetic  acid. 
The  liquid  is  neutralized  with  calcium  hydroxide  and  distilled,  when 
methyl  alcohol,  water,  etc.,  evaporate  and  a  solid  residue  is  left,  which 
is  an  impure  calcium  acetate.  From  this  latter,  acetic  acid  is  obtained 
by  distilling  with  sulphuric  (or  hydrochloric)  acid,  calcium  sulphate 
(or  chloride)  being  formed  and  left  in  the  retort,  whilst  acetic  acid 
distils  over. 

Experiment  46.  Add  to  54  grammes  of  sodium  acetate  contained  in  a  small 
flask  which  is  connected  with  a  Liebig's  condenser,  40  grammes  of  sulphuric 


MONOBASIC  FATTY  ACIDS.  327 

acid.    Apply  heat  and  distil  over  about  35  c.c.     Determine  volumetrically  the 
amount  of  pure  acetic  acid  in  this  liquid. 

Pure  acetic  acid,  or  glacial  acetic  acid,  is  solid  at  or  below  15°  C. 
(59°  F.);  at  higher  temperatures  it  is  a  colorless  liquid  having  a 
characteristic,  penetrating  odor,  boiling  at  118°  C.  (224°  F.),  and 
causing  blisters  on  the  skin  ;  its  specific  gravity  is  1.056  ;  it  is  misci- 
ble  with  water,  alcohol,  and  ether,  is  strongly  acid,  forming  salts 
known  as  acetates,  which  are  all  soluble  in  water. 

Vinegar  is  dilute  acetic  acid  (about  6  per  cent.),  containing  often 
other  substances,  such  as  coloring  matter,  compound  ethers,  etc. 
Vinegar  was  formerly  obtained  exclusively  by  the  oxidation  of  fer- 
mented fruit-juices  (wine,  cider,  etc.),  the  various  substances  present 
in  them  imparting  a  pleasant  taste  and  odor  to  the  vinegar ;  to-day 
vinegar  is  often  made  artificially  by  adding  various  coloring  and 
odoriferous  substances  to  dilute  acetic  acid.  Vinegar  should  be  tested 
for  sulphuric  and  hydrochloric  acids,  which  are  sometimes  fraudu- 
lently added. 

Acidum  aceticum,  Acidum  aceticum  dilutum,  and  Acidum  aceticum 
glaciate  are  the  three  official  forms  of  acetic  acid.  The  first-named 
acid  contains  36  per  cent.,  the  second  6  per  cent.,  the  third  at  least  99 
per  cent,  of  pure  acetic  acid. 

Acetic  acid  shows  an  exceptional  behavior  in  regard  to  the  specific 
gravity  of  its  aqueous  solutions.  The  highest  specific  gravity  of 
1.0748  belongs  to  an  acid  of  78  per  cent.,  which  is  equal  to  an  acid 
•containing  one  molecule  of  water  and  one  of  acetic  acid,  or  C2H4O2.H2O. 
The  addition  of  either  acetic  acid  or  of  water  causes  the  liquid  to 
become  lighter.  For  instance,  the  specific  gravity  of  an  acid  contain- 
ing 95  per  cent,  is  equal  to  that  containing  56  per  cent,  of  pure  acid, 
both  solutions  having  a  specific  gravity  of  1.066. 

The  specific  gravity  of  dilute  acetic  acid  cannot,  therefore,  be  used 
as  a  means  of  determining  the  amount  of  pure  acid  ;  this  is  done  by 
exactly  neutralizing  a  weighed  portion  of  the  acid  with  an  alkali ; 
from  the  quantity  of  the  latter  used,  the  quantity  of  actual  acid  present 
may  be  easily  calculated.  (See  also  volumetric  methods  in  Chapter 
37.) 

Analytical  reactions. 
(Sodium  acetate,  NaC2H3O2,  may  be  used.) 

1.  Any  acetate  heated  with  sulphuric  acid  evolves  acetic  acid, 
which  may  be  recognized  by  its  odor. 


328  CONSIDERATION  OF  CARBON  COMPOUNDS. 

2.  Acetic  acids  or  acetates  heated  with  sulphuric  acid  and  alcohol 
give  a  characteristic  odor  of  acetic  ether. 

3.  A  solution  containing  acetic  acid,  or  an  acetate  carefully  neutral- 
ized, turns  deep  red  on  the  addition  of  solution  of  ferric  chloride, 
and  forms,  on  boiling,  a  reddish-brown  precipitate  of  an  oxyacetate 
of  iron. 

Potassium  acetate,  Potassii  acetas,  KC2H3O2  =  98.  Sodium 
acetate,  Sodii  acetas,  NaC2H3O2.3H2O  =  136.  Zinc  acetate, 
Zinci  acetas,  Zn  (C2H3O2)2.2H2O  =  219.  These  three  salts  may  be 
obtained  by  neutralizing  the  respective  carbonates  with  acetic  acid 
and  evaporating  the  solution  ;  they  are  white  salts,  easily  soluble  in 
water. 

Ammonium  acetate,  NH4C2H3O2,  is  official  in  the  form  of  a  7 
per  cent,  solution,  which  is  known  as  Spirit  of  Mindererus. 

Ferric  acetate,  Fe2(C2H3O2)6.  A  33  per'  cent,  solution  of  this  salt 
is  the  Liquor  ferri  acetatis  of  the  U.  S.  P.  It  is  made  by  dissolving 
freshly  precipitated  ferric  hydroxide  in  acetic  acid ;  it  is  a  dark,  red- 
brown,  transparent  liquid  of  a  specific  gravity  of  1.16. 

Lead  acetate,  Plumbi  acetas,  Pb(C2H3O2)23H2O  =  378.4  (Sugar 
of  lead\  is  made  by  dissolving  lead  oxide  in  diluted  acetic  acid.  It 
forms  colorless,  shining,  transparent  crystals,  easily  soluble  in  water; 
on  heating,  it  melts  and  then  loses  water  of  crystallization ;  at  yet 
higher  temperatures  it  is  decomposed ;  it  has  a  sweetish,  astringent, 
afterward  metallic  taste.  Commercial  sugar  of  lead  contains  often  an 
excess  of  lead  oxide  in  the  form  of  basic  salts ;  such  an  article  when 
dissolved  in  spring  water  gives  generally  a  turbid  solution,  in  conse- 
quence of  the  formation  of  lead  carbonate ;  the  addition  of  a  few 
drops  of  acetic  acid  renders  the  liquid  clear  by  dissolving  the  pre- 
cipitate. 

When  a  mixture  of  lead  acetate  and  lead  oxide  is  digested  or  boiled 
with  water,  the  acetate  combines  with  the  oxide,  forming  a  basic  lead 
acetate,  approximately  Pb(C2H3O2)2.PbO,  a  25  per  cent,  solution  of 
which  is  the  Liquor  plumbi  subacetatis,  or  Goulard's  extract,  whilst  a 
solution  containing  about  1  per  cent,  is  the  Liquor  plumbi  subacetatis 
dilutus,  or  lead-water. 

Cupric  acetate,  Cu(C2H3O2)2H2O.  The  commercial  verdigris  is  a 
basic  acetate  of  copper,  Cu(C2H3O2)2CuO,  made  by  the  action  of 
dilute  acetic  acid  and  atmospheric  air  on  metallic  copper.  By  adding 


MONOBASIC  FA  TTY  A  CIDS.  329 

to  this  basic  acetate  more  acetic  acid,  the  neutral  acetate  is  obtained, 
but  this  may  be  made  directly  also  by  dissolving  cupric  hydroxide 
or  carbonate  in  acetic  acid.  It  forms  deep  green,  prismatic  crystals, 
which  are  soluble  in  water. 

By  boiling  verdigris  with  arsenous  oxide,  cupric  aceto-arsenite, 
3CuAs2O4  +  Cu(C2H3O2)2,  is  formed,  which  is  the  chief  constituent 
of  emerald  green  or  Schweinfurt  green,  a  substance  often  used  as  a 
coloring  matter.  Paris  green  is  of  a  similar  composition,  but  less 
pure. 

Ciller-acetic  acids.  By  treating  acetic  acid  with  chlorine,  either  one,  two, 
or  three  hydrogen  atoms  may  be  replaced  by  this  element,  when  either  mono-, 
di-,  or  tri-chlor-acetic  acid  is  formed.  Trichlor-acetic  acid,  C2C13HO2,  is  a  color- 
less, crystalline  substance,  which  fuses  at  55°  (131°  F.),  and  boils  at  195°  C. 
(383°  F.). 

Acetone,  C3H6O  (Dimethyl -ketone).  This  compound  is  obtained 
by  the  destructive  distillation  of  acetates  (and  of  a  number  of  other 
substances).  The  decomposition  which  calcium  acetate  suffers  may 
be  shown  by  the  equation : 

CH3COO\C    ._  CH3\CO    ,    c  co 
CH3COOX  CH3x  3> 

Calcium  acetate.          Acetone. 

The  above  graphic  formula  of  acetone  shows  this  substance  to  be 
dimethyl  carbonyl,  or  carbon  monoxide  whose  two  available  affini- 
ties have  been  satisfied  by  two  methyl  groups.  Acetone  is  the  repre- 
sentative of  a  series  of  compounds  known  as  acetones  or  generally 
as  ketoneSj  the  general  composition  of  which  may  be  assumed  to  be 
R_C— E 

||        ,  II  representing  in  this  case  any  univalent  radical. 
O 

Acetone  is  a  colorless  liquid,  boiling  at  58°  C.  (136°  F.),  miscible 
with  water,  alcohol,  and  ether  in  all  proportions ;  it  has  a  peculiar 
ethereal,  somewhat  mint-like  odor. 

Butyric  acid,  HC4H702.  Among  the  glycerides  of  butter  those  of  butyric 
acid  are  found ;  they  exist  also  in  cod-liver  oil,  croton  oil,  and  a  few  other  fatty 
oils ;  some  volatile  oils  contain  compound  ethers  of  butyric  acid ;  free  butyric 
acid  occurs  in  sweat  and  in  cheese.  It  may  be  obtained  by  a  peculiar  fermen- 
tation of  lactic  acid  (which  itself  is  a  product  of  fermentation),  and  is  also 
generated  during  the  putrefaction  of  albuminous  substances.  Butyric  acid  is 
a  colorless  liquid,  having  a  characteristic,  unpleasant  odor;  it  mixes  with 
water  in  all  proportions. 

Valerianic  acid,  HC5H9O2  ( Valeric  acid).  This  acid  occurs  in 
valerian  root  and  angelica  root,  from  which  it  may  be  separated ;  it 


330  CONSIDERATION  OF  CARBON  COMPOUNDS. 

is,  however,  generally  obtained  by  oxidation  of  amyl  alcohol  by 
potassium  dichromateand  sulphuric  acid.  After  oxidation  has  taken 
place  the  mixture  is  distilled,  when  valerianic  acid  with  some 
valerianate  of  amyl  distils  over.  The  change  of  amyl  alcohol  into 
valerianic  acid  is  analogous  to  the  conversion  of  ethyl  alcohol  into 
acetic  acid : 

C5HnOH     +     2O    ==    HC5H902     +     H20. 
Amyl  alcohol.  Valerianic  acid. 

Pure  valerianic  acid  is  an  oily,  colorless  liquid,  having  a  penetrat- 
ing, highly  characteristic  odor ;  it  is  slightly  soluble  in  water,  but 
soluble  in  alcohol ;  it  boils  at  185°  C.  (365°  F.). 

Several  of  the  salts  of  valerianic  acid  are  official ;  they  are  the 
valerianate  of  iron,  of  ammonium,  of  zinc,  and  of  quinine.  The  last 
named  three  compounds  are  white  salts,  while  the  ferric  valerianate 
has  a  dark-red  color ;  the  ammonium  salt  is  easily  soluble  in  water, 
the  other  three  compounds  are  insoluble  or  nearly  so. 

Oleic  acid,  Acidum  oleicum,  HC18H33O2  =  282.  As  shown  by 
its  formula,  oleic  acid  does  not  belong  to  the  above-described  series  of 
fatty  acids  of  the  composition  CnH2nO2,  but  to  a  series  having  the 
general  composition  CnH2n_2O2. 

Oleic  acid  is  a  constituent  of  most  fats,  especially  of  fat  oils.  Thus, 
olive  oil  is  mainly  oleate  of  glyceril.  By  boiling  olive  oil  with 
potassium  hydroxide,  potassium  oleate  is  formed,  which  may  be 
decomposed  by  tartaric  acid,  when  oleic  acid  is  liberated. 

Oleic  acid  is  a  nearly  colorless,  yellowish,  or  brownish-yellow, 
odorless,  tasteless,  neutral  oily  liquid,  insoluble  in  water,  soluble  in 
alcohol,  chloroform,  oil  of  turpentine,  and  fat  oils,  crystallizing  near 
the  freezing-point  of  water;  exposed  to  the  air  it  decomposes  and 
shows  then  an  acid  reaction.  Lead  oleate  is  soluble  in  ether,  lead 
palmitate  and  lead  stearate  are  not. 

The  official  oleates  of  mercury ,  zinc,  and  veratrine  are  obtained  by 
dissolving  the  yellow  mercuric  oxide,  zinc  oxide,  or  veratrine  in 

oleic  acid. 

_» 

QUESTIONS. — 421.  What  is  the  constitution  of  organic  acids,  which  group 
of  atoms  is  found  in  all  of  them,  and  how  does  an  alcohol  radical  differ  from 
an  acid  radical  ?  422.  Give  some  processes  by  which  organic  acids  are  formed 
in  nature  or  artificially.  423.  Mention  the  general  properties  of  organic 
acids.  424.  Which  series  of  acids  is  known  as  fatty  acids,  and  why  has  this 
name  been  given  to  them  ?  425.  Mention  names,  composition,  and  occurrence 
in  nature  of  the  first  five  members  of  the  series  of  fatty  acids.  426.  By  what 


DIBASIC  AND  TRIBASIC  ACIDS.  331 

44.   DIBASIC   AND  TRIBASIC   ORGANIC  ACIDS. 
Dibasic  acids  of  the  general  composition  CnH2a-2O4. 

Oxalic  acid H2C2O4      ™          (CO2H)2. 

Malonicacid      .        .         .        .        .  H2C3H2O4  or  C  H,(CO2H)2. 

Succinicacid H2C4H4O4  or  C.2H4(CO2H)2. 

Pyrotartaric  acid        ....  H2C5H6O4  or  C3H6(  CO2H)2. 

Adipicacid H2C6H804orC4H8(C02HV 

etc. 

Of  these  acids,  only  the  first  member  is  of  general  interest. 

Oxalic  acid,  H2C2O4.2H2O.  This  acid  may  be  looked  upon  as  a 
direct  combination  of  two  carboxyl  groups,  CO2H — CO2H,  both 
atoms  of  hydrogen  being  replaceable  by  metals. 

Oxalic  acid  is  distributed  largely  in  the  vegetable  kingdom  in  the 
form  of  potassium,  sodium,  or  calcium  salts.  It  may  be  obtained 
from  vegetables,  or  by  the  oxidation  of  many  organic  substances, 
chiefly  fats,  sugars,  starch,  etc.,  by  nitric  acid  or  other  strong  oxidiz- 
ing agents. 

Experiment  74.  Pour  a  mixture  of  15  c.c.  nitric  acid  and  35  c.c.  of  water 
upon  10  grammes  of  sugar  contained  in  a  200  c.c.  flask.  Apply  heat  gently 
until  the  reaction  begins.  When  red  fumes  cease  to  escape  pour  the  solution 
into  a  porcelain  dish  and  evaporate  to  about  one-half  its  volume.  Crystals  of 
oxalic  acid  separate  on  cooling ;  use  them  for  making  the  analytical  reactions 
mentioned  below. 

Oxalic  acid  is  manufactured  on  the  large  scale  by  heating  sawdust 
with  potassium  or  sodium  hydroxide  to  about  250°  C.  (482°  F.), 
when  the  oxalate  of  these  metals  is  formed ;  by  the  addition  of  cal- 
cium hydroxide  to  the  dissolved  alkali  oxalate,  insoluble  calcium 
oxalate  is  formed  which  is  decomposed  by  sulphuric  acid. 

Oxalic  acid  crystallizes  in  large,  transparent,  colorless  prisms,  con- 
taining two  molecules  of  water  ;  it  is  soluble  in  water  and  alcohol, 
and  has  poisonous  properties.  When  heated  slowly,  it  sublimes  at  a 

processes  may  formic  acid  be  obtained,  and  what  are  its  properties?  427. 
Describe  the  processes  of  manufacturing  acetic  acid  from  alcohol  and  from 
wood.  428.  What  is  vinegar,  and  what  is  glacial  acetic  acid  ?  Give  tests  for 
acetic  acid  and  for  acetates.  429.  Describe  the  processes  for  making  the 
acetates  of  potassium,  zinc,  iron,  lead,  and  copper,  and  also  of  Goulard's  ex- 
tract and  lead-water ;  state  their  composition  and  properties.  430.  When  and 
in  what  form  of  combination  is  oleic  acid  found  in  nature,  and  what  are  its 
properties  ? 


332  CONSIDERATION  OF  CARBON  COMPOUNDS. 

temperature  of  about  155°  C.  (311°  F.)  ;  but  if  heated  higher  or  with 
sulphuric  acid  it  is  decomposed  into  water,  carbonic  oxide,  and  carbon 

dioxide  : 

H2C204    :       H20    +    CO    +    CO2. 

Oxalic  acid  acts  as  a  reducing  agent,  decolorizing  solutions  of  the 
permanganates,  and  precipitating  gold  and  platinum  from  their  solu- 

tions : 

PtCl4  +  2H2C2O4  =  Pt  +  4CO2  +  4HC1. 

Analytical  reactions. 
(Sodium  oxalate,  Na2C2O4,  may  be  used.) 

1.  Oxalic  acid  or  oxalates  when  heated  with  strong  sulphuric  acid 
evolve  carbonic  oxide  and  carbon  dioxide  (see  above). 

2.  Neutral  solutions  of  oxalic  acid  give  with  calcium  chloride  a 
white  precipitate  of  calcium  oxalate,  CaC2O4,  which  is  insoluble  in 
acetic,  soluble  in  hydrochloric  acid. 

3.  Silver  nitrate  produces  a  white  precipitate  of  silver  oxalate, 
Ag2C204. 

4.  A  dry  oxalate  (containing  a  non-volatile  metal)  heated  in  a  test- 
tube  evolves  carbonic  oxide,  whilst  a  carbonate  is  left  which  shows 
effervescence  with  acids. 

Antidotes  to  oxalic  acid.  Calcium  carbonate  or  lime-water  should  be  admin- 
istered, but  no  alkalies  as  in  cases  of  poisoning  by  mineral  acids,  because  the 
alkali  oxalates  are  soluble. 

Oxalates.  The  acid  potassium  oxalate,  KHC2O4,  or  its  combina- 
tion with  oxalic  acid,  is  known  under  the  name  of  salt  of  sorrel. 
Calcium  oxalate,  CaC2O4,  is,  in  small  quantities,  a  normal  constituent 
of  urine.  Ferrous  oxalate,  FeC2O4.H2O,  is  made  by  adding  potas- 
sium or  ammonium  •  oxalate  to  ferrous  sulphate,  when  double  decom- 
position takes  place,  and  the  ferrous  oxalate  is  precipitated  as  a  pale- 
yellow,  crystalline,  nearly  insoluble  powder. 

Dibasic  acids  with  alcoholic  hydroxyl. 

/OH 


Malic  acid  =  C4H6O5  or  C2H3CO2H 

2 


XC0H 


//OH. 

Tartaric  acid  ==  C4H6O6  or  C2H2 


In  the  various  acids  heretofore  considered,  the  hydrogen  is  derived 
either  from  the  unsaturated  hydrocarbon  residue,  or  from  the  hydroxyl 


DIBASIC  AND  TRIBASIC  ACIDS,  333 

in  the  carboxjl.  As  shown  by  the  graphic  formulas  of  the  above 
two  acids,  they  contain  also  hydrogen  in  the  hydroxyl  form  not  in 
combination  with  CO.  This  hydrogen,  whilst  not  replaceable  by 
metals,  may  be  replaced  by  alcohol  radicals ;  in  other  words,  it  be- 
haves like  the  hydroxyl  hydrogen  in  alcohols.  In  order  to  indicate 
this  difference  in  the  function  of  the  hydrogen,  malic  acid  is  said  to  be 
dibasic,  but  triatomic  ;  tartaric  acid  is  dibasic  and  tetratomic.  A  few 
other  acids  behave  in  a  similar  manner,  as,  for  instance,  lactic  ac!d. 

Malie  add,  H2C4H4O5,  occurs  in  the  juices  of  many  fruits,  as 
apples,  currants,  etc. 

Tartaric  acid,  Acidum  tartaricum,  H2C4H4O6  =  15O.  Frequently 
found  in  vegetables,  and  especially  in  fruits,  sometimes  free,  generally 
as  the  potassium  or  calcium  salt ;  grapes  contain  it  chiefly  as  potas- 
sium acid  tartrate,  which  is  obtained  in  an  impure  state  as  a  by- 
product in  the  manufacture  of  wine.  During  the  fermentation  of 
grape-juice,  its  sugar  is  converted  into  alcohol ;  potassium  acid  tar- 
trate is  less  soluble  in  alcoholic  fluids  than  in  water,  and  therefore  is 
deposited  gradually,  forming  the  crude  tartar,  or  argol,  of  commerce, 
a  substance  containing  chiefly  potassium  acid  tartrate,  but  also  cal- 
cium tartrate,  some  coloring  matter,  and  traces  of  other  substances. 
Crude  tartar  is  the  source  of  tartaric  acid  and  its  salts. 

Tartaric  acid  is  obtained  from  potassium  acid  tartrate  by  neutral- 
izing with  calcium  carbonate,  and  decomposing  the  remaining  neutral 
potassium  tartrate  by  calcium  chloride  : 

2(KHC4H406)  +  CaCO3  =  CaC4H4O6  +  K2C4H4O6  +  H2O  +  CO2. 
Potassium  acid         Calcium          Calcium  Potassium        Water.      Carbon 

tartrate.  carbonate.         tartrate.  tartrate.  dioxide. 

K2C4H4O6  +  CaCl2  ==  CaC4H4O6  -f  2KC1. 
Potassium        Calcium          Calcium         Potassium 
tartrate.         chloride.  tartrate.  chloride. 

The  whole  of  the  tartaric  acid  is  thus  converted  into  calcium  tar- 
trate, which  is  precipitated  as  an  insoluble  powder ;  this  is  collected, 
well  washed,  and  decomposed  by  boiling  with  sulphuric  acid,  when 
calcium  sulphate  is  formed  as  an  almost  insoluble  residue,  while  tar- 
taric acid  is  left  in  solution,  from  which  it  is  obtained  by  evaporation 
and  crystallization  : 

CaC4H406  +  H2S04  =  H2C4H4O6  +  CaSO4. 
Calcium          Sulphuric          Tartaric  Calcium 

tartrate.  acid.  acid.  sulphate. 

Tartaric  acid  crystallizes  in  colorless,  transparent  prisms ;  it  has  a 
strongly  acid,  but  not  disagreeable  taste ;  it  is  readily  soluble  in  water 
and  alcohol,  and  fuses  at  135°  C.  (275°  F.). 


334  CONSIDERATION  OF  CARBON  COMPOUNDS. 

There  are  three  acids  which  are  isomeric  with  common  tartaric 
acid,  differing  from  it  in  physical,  but  not  in  chemical  properties. 
These  acids  are  known  as  inactive  tartaric  acid,  levotartaric  acid,  and 
racemic  acid,  whilst  the  common  tartaric  acid  is  termed  dextrotartaric 
acid.  Crude  tartar  sometimes  contains  racemic  acid. 

Analytical  reactions. 
(Potassium  sodium  tartrate,  KNaC4H4O6,  may  be  used.) 

1.  Neutral  solutions  of  tartaric  acid  give  with  calcium  chloride  a 
white  precipitate  of  calcium  tartrate,  which,  after  being  quickly  col- 
lected on  a  filter  and  washed,  is  soluble  in  potassium  hydroxide  ;  from 
this  solution  calcium  tartrate  is  precipitated  on  boiling.     (Calcium 
citrate  is  insoluble  in  potassium  hydroxide.) 

2.  A  strong  solution  of  a  tartrate,  acidulated  with  acetic  acid,  gives 
a  white  precipitate  of  potassium  acid  tartrate  on  the  addition  of  potas- 
sium acetate.     (Precipitate  forms  slowly.) 

3.  A  neutral  solution  of  a  tartrate  gives  with  silver  nitrate  a  white 
precipitate  of  silver  tartrate,  Ag2C4H4O6,  which  blackens  on  boiling, 
in  consequence  of  the  decomposition  of  the  salt,  with  separation  of 
silver.     If,  before  boiling,  a  drop  of  ammonia  water  be  added,   a 
mirror  of  metallic  silver  will  form  upon  the  glass. 

4.  Sulphuric  acid  heated  with  tartrates  chars  them  readily. 

5.  Tartrates,  when  heated,  are  decomposed  (blacken),  and  evolve  a 
somewhat  characteristic  odor,  resembling  that  of  burnt  sugar 

The  above  reaction,  3,  can  be  used  to  advantage  for  silvering  glass  by  operat- 
ing as  follows:  Dissolve  1  gramme  of  silver  nitrate  in  20  c.c.  of  water,  add 
water  of  ammonia  until  the  precipitate  which  forms  is  nearly  redissolved,  and 
dilute  with  water  to  100  c.c.  Make  a  second  solution  by  dissolving  0.2  gramme 
of  silver  nitrate  in  100  c.c.  of  boiling  water,  add  0.166  gramme  of  potassium 
sodium  tartrate,  boil  until  the  precipitate  becomes  gray,  and  filter.  Mix  the 
two  solutions  cold  and  set  aside  for  one  hour,  when  a  mirror  of  metallic  silver 
will  be  found. 

Potassium  acid  tartrate,  Potassii  bitartras,  KHC4H4O6  =  188 
(Potassium  bitartrate,  Cream  of  tartar).  The  formation  of  this  salt  in 
the  crude  state  (argol)  has  been  explained  above.  It  is  purified  by 
dissolving  in  hot  water  and  crystallizing,  when  it  is  obtained  in  color- 
less crystals,  or  as  a  white,  somewhat  gritty  powder  of  a  pleasant, 
acidulous  taste;  it  is  sparingly  soluble  in  cold,  easily  soluble  in  hot 
water. 

The  name  cream  of  tartar  was  given  to  the  salt  for  the  reason  that 


DIBASIC  AND  TRIBASIC  ACIDS.  335 

small  crystals,  which  float  on  the  liquid,  separate  on  rapidly  cooling 
a  hot  solution  of  potassium  bitartrate. 

Potassium  tartrate,  2(K2C4H406).H.,0.  Obtained  by  saturating  a  solution 
of  potassium  acid  tartrate  with  potassium  carbonate : 

2KHC4H406  +  K2C03  =  2K2C4H4O6  +  H2O  +  CO2. 
Potassium  acid       Potassium        Potassium 
tartrate.  carbonate.          tartrate. 

Small  transparent  or  white  crystals,  or  a  white  neutral  powder,  soluble  in 
less  than  its  own  weight  of  water. 

Potassium  sodium  tartrate,  Potassii  et  sodii  tartras, 
KNaC4H4O6.4H20  =  282  (Rochelle  salt).  If  in  the  above-described 
process  for  making  neutral  potassium  tartrate,  sodium  carbonate  is 
substituted  for  potassium  carbonate,  the  double  tartrate  of  potassium 
and  sodium  is  formed.  It  is  a  white  powder,  or  occurs  in  colorless, 
transparent  crystals  which  are  easily  soluble  in  water. 

Experiment  48.  Add  gradually  24  grammes  of  potassium  acid  tartrate  to  a 
hot  solution  of  20  grammes  of  crystallized  sodium  carbonate  in  100  c.c.  of 
water.  ,  Heat  until  complete  solution  has  taken  place,  filter,  evaporate  to  about 
one-half  the  volume,  and  set  aside  for  the  potassium  sodium  tartrate  to  crys- 
tallize. How  much  crystallized  sodium  carbonate  is  required  for  the  conversion 
of  25  grammes  of  potassium  acid  tartrate  into  Rochelle  salt  ? 

Seidlitz  powders  (  Compound  effervescing  powders)  consist  of  a  mixture 
of  7.75  grammes  (120  grains)  of  Rochelle  salt  with  2.58  grammes 
(40  grains)  of  sodium  bicarbonate  (wrapped  in  blue  paper),  and  2.25 
grammes  (35  grains)  of  tartar ic  acid  (wrapped  in  white  paper). 
When  dissolved  in  water  the  tartaric  acid  acts  upon  the  sodium 
bicarbonate,  causing  the  formation  of  sodium  tartrate,  while  the 
escaping  carbon  dioxide  causes  effervescence. 

Antimony  and  potassium  tartrate,  Antimonii  et  potassii 
tartras,  2(KSbO.C4H4O6).H2O  =  664  (Potassium  antimonyl  tartrate, 
Tartar  emetic).  This  salt  is  made  by  dissolving  freshly  prepared 
antimonous  oxide  (while  yet  moist)  in  a  solution  of  potassium  acid 
tartrate.  From  the  solution  somewhat  evaporated,  tartar  emetic 
separates  in  colorless,  transparent  rhombic  crystals  : 

2KHC4H406     +     Sb203    =   =    2KSbO.C4H4O6    +     H2O. 

Potassium  acid        Antimonous  Tartar  emetic, 

tartrate.  oxide. 

The  fact  that  not  antimony  itself,  but  the  group  SbO,  replaces  the 
hydrogen,  has  led  to  the  assumption  of  the  hypothetical  radical  SbO> 
termed  antimonyl. 


336  CONSIDERATION  OF  CARbON  COMPOUNDS. 

Tartar  emetic  is  soluble  in  water,  insoluble  in  alcohol  ;  it  has  a 
sweet,  afterward  disagreeable  metallic  taste. 

Action  of  certain  organic  acids  upon  certain  metallic  oxides. 
The  solution  of  a  ferric  salt  (or  certain  other  metallic  salts)  is  pre- 
cipitated by  alkali  hydroxides,  a  salt  of  the  alkali  and  ferric  hydroxide 
being  formed.  When  a  sufficient  quantity  of  either  tartaric,  citric, 
oxalic,  or  various  other  organic  acids  has  been  added  previously  to 
the  iron  solution  (or  to  certain  other  metallic  solutions)  no  such  pre- 
cipitate is  produced  by  the  alkali  hydroxides,  because  organic  salts 
or  double  salts  are  formed  which  are  soluble,  and  from  which  the 
metallic  hydroxides  are  not  precipitated  by  alkali  hydroxides.  Upon 
evaporation  no  crystals  (of  the  organic  salt)  form,  and  in  order  to 
obtain  the  compounds  in  a  dry  state,  the  liquid,  after  being  evaporated 
to  the  consistence  of  a  syrup,  is  spread  on  glass  plates  which  are 
exposed  to  a  temperature  not  exceeding  60°  C.  (140°  F.),  when 
brown,  green,  or  yellowish-green,  amorphous,  shining,  transparent 
scales  are  formed,  which  are  the  scale  compounds  of  the  U.  S.  P. 

Instead  of  obtaining  these  compounds,  as  stated  above,  by  adding 
the  organic  acids  (or  their  salts)  to  the  inorganic  salts,  they  are  more 
generally  obtained  by  dissolving  the  freshly  precipitated  metallic 
hydroxide  in  the  organic  acid. 

The  true  chemical  constitution  of  many  of  these  scale  compounds 
has  as  yet  not  been  determined  with  certainty. 

Of  official  scale  compounds  containing  tartaric  acid  may  be  men- 
tioned the  iron  and  ammonium  tartraie,  and  the  iron  and  potassium 
tartrate.  The  first  compound  is  obtained  by  dissolving  freshly 
precipitated  ferric  hydroxide  in  a  solution  of  ammonium  acid  tartrate, 
the  second  by  dissolving  ferric  hydroxide  in  potassium  acid  tartrate. 
The  clear  solutions,  after  having  been  sufficiently  evaporated,  are 
dried,  as  mentioned  above,  on  glass  plates. 

Citric  acid,  Acidum  citricum,  H3C6H5O7.H2O  =  210.  Citric 
acid  is  a  tribasic  acid  containing  three  atoms  of  hydrogen  replaceable 
by  metals  ;  its  constitution  may  be  expressed  by  the  graphic  formula  : 

OH 


C3H4 

^ 

XC02H 

Citric  acid  is  found  in  the  juices  of  many  fruits  (strawberry,  rasp- 
berry, currant,  cherry,  etc.),  and  in  other  parts  of  plants.     It  is 


DIBASIC  AND  TRIBASIC  ORGANIC  ACIDS.  337 

obtained  from  the  juice  of  lemons  by  saturating  it  with  calcium  car- 
bonate and  decomposing  by  sulphuric  acid  the  calcium  citrate  thus 
formed.  (100  parts  of  lemons  yield  about  5  parts  of  the  acid.)  It 
forms  colorless  crystals,  easily  soluble  in  water. 

Analytical  reactions. 
(Potassium  citrate,  K3C6H5O7,  may  be  used.) 

1.  Neutral  solutions  of  citrates  yield  with  calcium  chloride  on 
boiling  (not  in  the  cold)  a  white  precipitate  of  calcium  citrate,  which 
is  insoluble  in  potassium  hydroxide,  but  soluble  in  cupric  chloride. 

2.  Neutral  solutions  of  citrates  are  precipitated  white  by  silver 
nitrate.     The  precipitate  does  not  blacken  on  boiling,  as  in  the  case 
of  tartrates. 

3.  A  neutral  or  alkaline  solution  of  a  citrate  to  which  a  few  drops 
of  a  solution  of  potassium  permanganate  have  been  added,  becomes 
green  or  reddish-green.     Tartrates  decolorize  permanganate. 

Citrates.  Potassium  citrate,  K3C6H5O7.H2O,  Lithium  citrate, 
Li3C6H5O7,  and  Magnesium  citrate,  Mg3(C6H5O7)2.14HO2,  are  color- 
less substances,  easily  soluble  in  water  and  obtained  by  dissolving 
the  carbonates  in  citric  acid. 

The  effervescent  citrates  of  potassium,  lithium,  and  magnesium,  are  granulated 
mixtures  of  citric  acid  with  potassium  bicarbonate,  lithium  carbonate,  and 
magnesium  carbonate  respectively ;  sugar  is  added  to  all,  and  some  sodium 
bicarbonate  to  the  two  last  preparations. 

The  official  solution  of  magnesium  citrate  is  made  by  dissolving  magnesium 
carbonate  in  an  excess  of  citric  acid  solution  to  which  some  syrup  is  added, 
and  dropping  into  this  mixture,  which  should  be  contained  in  a  strong  bottle, 
potassium  bicarbonate.  The  bottle  is  immediately  closed  with  a  cork  in  order 
to  retain  the  liberated  carbon  dioxide. 

Bismuth  citrate,  BiC6H5O7,  is  obtained  by  boiling  a  solution  of  citric  acid 
with  bismuth  nitrate,  when  the  latter  is  gradually  converted  into  citrate  whilst 
nitric  acid  is  set  free ;  the  insoluble  bismuth  citrate  is  collected,  washed,  and 
dried ;  it  forms  a  white,  amorphous  powder,  which  is  insoluble  in  water,  but 
soluble  in  water  of  ammonia. 

Bismuth  ammonium  citrate  is  a  scale  compound  obtained  by  dissolving  bismuth 
citrate  in  water  of  ammonia  and  evaporating  the  solution  at  a  low  temperature. 

Ferric  citrate,  Ferri  citras.  Obtained  in  transparent,  red  scales,  by  dissolving 
ferric  hydroxide  in  citric  acid  and  evaporating  the  solution  as  mentioned  here- 
tofore. By  mixing  solution  of  ferric  citrate  with  either  water  of  ammonia,  or 
quinine,  strychnine,  sodium  phosphate,  or  sodium  pyrophosphate,  evaporating 
to  the  consistence  of  syrup  and  drying  on  glass  plates,  the  following  scale  com- 
pounds are  obtained  respectively  :  Iron  and  ammonium  citrate,  iron  and  quinine 

22 


338  CONSIDERATION  OF  CARBON  COMPOUNDS. 

citrate,  iron  and  strychnine  citrate,  soluble  ferric  phosphate,  and  soluble  ferric  pyro- 
phosphate. 

Lactic  acid,  Acidum  lacticum,  HC3H5O3  =  9O.  This  acid  is 
the  second  member  of  a  group  of  monobasic,  diatomic  acids  which 
have  the  general  composition  CnH2DO3,  and  which  contain  two 
hydroxyl  groups,  the  hydrogen  of  one  being  capable  of  replacement 
by  metals,  the  other  by  alcohols.  The  first  member  of  this  series  is 
glycoliv  acid,  HC2H3O3,  a  white,  deliquescent,  crystalline  substance 
which  is  found  in  unripe  grapes  and  in  the  leaves  of  the  wild  grape. 
Glycolic  acid  has  been  shown  to  be  acetic  acid,  C2H4O2,  in  which  one 
atom  of  hydrogen  has  been  replaced  by  hydroxyl.  The  name 
hydroxy-acetic  acid,  has,  therefore,  been  given  to  this  compound. 

Lactic  acid  occurs  in  many  plant-juices ;  it  is  formed,  from  sugar 
by  a  peculiar  fermentation  known  as  "  lactic  fermentation,"  which 
causes  the  presence  of  this  acid  in  sour  milk  and  in  many  sour,  fer- 
mented substances,  as  in  ensilage,  sauer-kraut,  etc.  The  formation 
of  lactic  acid  from  sugar  may  be  expressed  by  the  equation : 

C6H1206    =    2(HC3H503). 
Sugar.  Lactic  acid. 

For  practical  purposes  lactic  acid  is  made  by  mixing  a  solution  of 
sugar  with  milk,  putrid  cheese,  and  chalk,  and  digesting  this  mixture 
for  several  weeks  at  a  temperature  of  about  30°  C.  (86°  F.).  The 
bacteria  in  the  cheese  act  as  a  ferment,  and  the  chalk  neutralizes  the 
acid  generated  during  the  fermentation.  The  calcium  lactate  thus 
obtained  is  purified  by  crystallization  and  decomposed  by  oxalic  acid, 
which  forms  insoluble  calcium  oxalate. 

Lactic  acid  is  a  colorless,  syrupy  liquid,  of  strongly  acid  properties ; 
it  mixes  in  all  proportions  with  water  and  alcohol.  The  official 
lactic  acid  contains  75  per  cent,  of  absolute  acid. 

A  lactic  acid  called  sarco-lactic  acid  is  found  in  meat-juice,  and,  therefore,  as 
a  constituent  of  meat-extract.  This  acid  has  the  composition  and  all  the 
properties  of  the  above  ordinary  lactic  acid,  with  the  exception  that  it  acts 
differently  on  polarized  light. 

Ferrous  lactate,  Ferri  lactas,  Fe(C3H503)2.3H20  =  287.9.  Made  by  dis- 
solving iron  filings  in  diluted  lactic  acid ;  hydrogen  is  liberated  and  the  salt 
formed.  It  is  a  pale,  greenish-white,  crystalline  substance,  soluble  in  water. 

QUESTIONS. — 431.  Name  the  more  common  organic  acids  found  in  vegeta- 
bles and  especially  in  sour  fruits.  432.  What  is  the  composition  of  oxalic  acid, 
how  is  it  manufactured,  and  what  are  its  properties  ?  433.  Explain  the  forma- 
tion of  crude  tartar  during  the  fermentation  of  grape-juice,  and  how  is  tartaric 


ETHERS.  339 

Strontium  lactate,  Sr(C3H503)2.3H20,  is  readily  obtained  by  dissolving 
strontium  carbonate  in  lactic  acid.  It  is  a  white  granular  or  crystalline 
powder,  readily  soluble  in  water. 

45.    ETHEKS. 

Constitution.  It  has  been  shown  that  alcohols  are  hydrocarbon 
residues  in  combination  with  hydroxyl,  OH,  and  that  acids  are  hydro- 
carbon residues  in  combination  with  carboxyl,  CO.OH  ;  it  has  further 
been  shown  that  carboxyl  may  be  considered  as  being  composed  of 
CO,  and  hydroxyl,  OH,  and  that  the  term  acid  radical  is  applied  to 
that  group  of  atoms  in  acids  which  embraces  the  hydrocarbon  residue 
-f-  CO.  If  we  represent  an  alcohol  radical  by  AIR,  and  an  acid 
radical  by  AcR,  the  general  formula  of  an  alcohol  is  A1R.OH,  or 

TT  /O,  and  of  an  acid,  AcR.OH,  or    ^  ^O. 

Ethers  are  formed  by  replacement  of  the  hydrogen  of  the  hydroxyl 
in  alcohols  by  hydrocarbon  residues  (or  alcohol  radicals),  and  com- 
pound ethers  or  esters  are  formed  by  replacement  of  the  hydrogen  of 
the  hydroxyl  (or  carboxyl)  in  acids  by  hydrocarbon  residues.  While 
alcohols  correspond  in  their  constitution  to  hydroxides,  ethers  corre- 
spond to  oxides,  and  compound  ethers  to  salts.  For  instance : 


Hydroxides. 

Oxides. 

Acids. 

Salts. 

KOH  =  g>0 

Potassium  hydroxide. 

Potassium  oxide. 

Nitric  acid. 

Potassium  nitrate. 

HX 

Ethyl  alcohol. 

C2H5\0 
C2H5XC 
Ethyl  ether. 

C!H!O\O 

Acetic  acid. 

C2H30\0 
C2H5x° 

Ethyl  acetate,  or 
acetic  ether. 

A1K\0 

A1K\0 
Affix0 

AcR\Q 

AcR\0 
Affix0' 

Alcohol.  Ether.  Acid.  Compound  ether. 

It  is  not  necessary  that  the  two  hydrocarbon  residues  in  an  ether 
should  be  alike,  as  in  the  above  ethyl  ether,  but  they  may  be  different, 
in  which  case  the  ethers  are  termed  mixed  ethers.  For  instance  : 

acid  obtained  from  it?  434.  Give  properties  of  and  tests  for  tartaric  acid. 
435.  State  the  composition  and  formation  of  cream  of  tartar,  Kochelle  salt, 
and  tartar  emetic.  436.  What  are  Seidlitz  powders,  and  what  changes  take 
place  when  they  are  dissolved  ?  437.  Mention  some  official  scale  compounds 
of  iron,  and  give  a  general  outline  of  the  mode  of  preparing  them.  438. 
From  what  and  by  what  process  is  citric  acid  obtained  ?  439.  Mention  tests 
by  which  citric  acid  may  be  distinguished  from  tartaric  acid.  440.  From 
what  and  by  what  process  is  lactic  acid  obtained ;  what  are  its  properties  ? 


340  CONSIDERATION  OF  CARBON  COMPOUNDS. 


CH3.C2H50  =  q35o         C3H7.C5Hn.O  - 

Methyl-ethyl  ether.  Propyl-amyl  ether. 

In  diatomic  or  triatomic  alcohols,  or  in  dibasic  or  tribasic  acids, 
containing  more  than  one  atom  of  hydrogen  derived  from  hydroxyl 
or  carboxyl,  these  hydrogen  atoms  may  be  replaced  by  various  other 
univalent,  bivalent,  or  trivalent  residues.  This  fact  shows  that  the 
number  of  ethers  or  compound  ethers  which  are  capable  of  being 
formed  is  very  large. 

Formation  of  ethers.  Ethers  may  be  formed  by  the  action  of 
the  chloride  or  iodide  of  a  hydrocarbon  residue  upon  an  alcohol,  in 
which  the  hydroxyl  hydrogen  has  been  replaced  by  a  metal.  For 
instance  : 


Sodium  ethylate.    Ethyl  iodide.       Ethyl  ether.    Sodium  iodide. 


o  +    CHSI     :  O  +  NaL 

Sodium  Methyl          Ethyl-methyl         Sodium 

ethylate.  iodide.  ether.  iodide. 

Ethers  are  also  formed  by  the  action  of  sulphuric  acid  upon  alco- 
hols ;  the  sulphuric  acid  removing  water  in  this  case,  thus  : 


2(C2H5OH)       : 

Ethyl  alcohol.          Ethyl  ether.  Water. 

Compound  ethers  are  formed  by  the  combination  of  acids  with 
alcohols  and  elimination  of  water.  (Presence  of  sulphuric  acids 
facilitates  this  action. 


+    H2o. 

Ethyl  alcohol.          Acetic  acid.  Ethyl  acetate.  Water. 

They  are  also  formed  by  the  action  of  hydrocarbon  chlorides  (or 
iodides)  on  salts.     For  instance  : 

C5HUC1    +    °HO     =  .   5°    +    KC1 


Amyl  Potassium  Amyl  Potassium 

chloride.  formate.  formate.  chloride. 

Occurrence  in  nature.  Many  ethers  are  products  of  vegetable 
life  and  occur  in  some  essential  oils;  wax  contains  the  compound 
ether  melissyl  palmitate,  C30H61.C16H31O.O,  and  spermaceti,  a  solid 
substance  found  in  the  head  of  the  whale,  is  cethyl  palmitate,  C16H33. 
C16H31O.O.  The  most  important  group  of  compound  ethers  are  the 
fats  and  fatty  oils,  which  are  distributed  widely  in  the  vegetable,  but 
even  more  so  in  the  animal  kingdom. 


ETHERS.  341 

General  properties.  The  ethers  and  compound  ethers  of  the 
lower  members  of  the  monatomic  alcohols  and  fatty  acids  have  gener- 
ally a  characteristic  and  pleasant  odor.  Fruit  essences  consist  mainly 
of  such  compound  ethers,  and  what  is  generally  known  as  the 
"bouquet"  or  "flavor"  of  wine  and  other  alcoholic  liquors  is  due 
chiefly  to  ethers  or  compound  ethers,  which  are  formed  during  (and 
after)  the  fermentation  by  the  action  of  the  acids  present  upon  the 
alcohol  or  the  alcohols  formed.  The  improvement  which  such  alco- 
holic liquids  undergo  "  by  age  "  is  caused  by  a  continued  chemical 
action  between  the  substances  named. 

All  ethers  are  neutral  substances  ;  those  formed  by  the  lower  alco- 
hols and  acids  are  generally  volatile  liquids,  those  of  the  higher 
members  are  non- volatile  solids.  When  compound  ethers  are  heated 
with  alkalies,  the  acid  combines  with  the  latter,  whilst  the  alcohol  is 
liberated.  (The  properties  of  the  compound  ethers,  termed  fats,  will 
be  considered  further  on.) 

Ethyl  ether,  u3Ether,  (C2H5)2O  =  74  (Ether,  sulphuric  ether,  Ethyl 
oxide).  The  name  of  the  whole  group  of  ethers  is  derived  from  this 
(ethyl-)  ether,  in  the  same  way  that  common  (ethyl-)  alcohol  has 
given  its  name  to  the  group  of  alcohols.  The  name  sulphuric  ether 
was  given  at  a  time  when  its  true  composition  was  yet  unknown,  and 
for  the  reason  that  sulphuric  acid  was  used  in  its  manufacture. 

Ether  is  manufactured  by  heating  to  about  140°  C.  (284°  F.)  a 
mixture  of  1  part  of  alcohol  and  1.8  parts  of  concentrated  sulphuric 
acid  in  a  retort,  which  is  so  arranged  that  additional  quantities  of 
alcohol  may  be  allowed  to  flow  into  it,  while  the  open  end  is  connected 
with  a  tube,  leading  through  a  suitable  cooler,  in  order  to  condense 
the  highly  volatile  product  of  the  distillation. 

Experiment  49.  Mix  100  grammes  of  alcohol  with  180  grammes  of  ordinary 
sulphuric  acid,  allow  to  stand  and  pour  the  cooled  mixture  into  a  flask  which 
is  provided  with  a  perforated  cork  through  which  pass  a  thermometer  and  a 
bent  glass  tube  leading  to  a  Liebig's  condenser.  Apply  heat  and  notice  that 
the  liquid  commences  to  boil  at  about  140°  C.  (284°  F.).  Distil  about  50  c.c., 
pour  this  liquid  into  a  stoppered  bottle  and  add  an  equal  volume  of  water. 
Ethyl  ether  will  separate  into  a  distinct  layer  over  the  water,  and  may  be 
removed  by  means  of  a  pipette.  Repeat  the  washing  with  water,  add  to  the 
ether  thus  freed  from  alcohol  a  little  calcium  chloride  and  distil  it  from  a  dry 
flask,  standing  in  a  water-bath.  The  greatest  care  should  be  exercised  and  the 
neighborhood  of  flames  avoided  in  working  with  ether,  on  account  of  its 
volatility  and  the  inflammability  of  its  vapors. 

The  apparatus  described  above  for  etherification  can  be  constructed  so  as  to 
make  the  process  continuous.  This  may  be  done  by  using  with  the  boiling- 


342  CONSIDERATION  OF  CARBON  COMPOUNDS. 

flask  a  cork  with  a  third  aperture  through  which  a  glass  tube  passes  into  the 
liquid.  The  other  end  of  the  tube  is  connected  by  means  of  rubber  tubing 
with  a  vessel  filled  with  alcohol  and  standing  somewhat  above  the  flask.  As 
soon  as  distillation  commences  alcohol  is  allowed  to  flow  into  the  flask  at  a 
rate  equal  to  that  of  the  distillation,  keeping  the  temperature  at  about  140°  C. 
(284°  F.).  The  flow  of  alcohol  is  regulated  by  a  stop-cock.  . 

The  action  of  sulphuric  acid  upon  alcohol  is  not  quite  so  simple  as 
described  above  in  connection  with  the  general  methods  for  obtaining 
ethers,  where  the  final  result  only  was  given  An  intermediate  pro- 
duct, known  as  ethyl- sulphuric  acid  or  sulpho-vinic  acid,  is  formed, 
which,  by  acting  upon  another  molecule  of  alcohol,  forms  sulphuric 
acid  and  ether,  which  latter  is  volatilized  as  soon  as  formed.  The 
decomposition  is  shown  by  the  equations  : 

C2H5OH    +     H2S04  .==    C2H5HS04     +     H2O. 

Alcohol.  Sulphuric        Ethyl-sulphuric         Water, 

acid.  acid. 

C2H5HSO,    +     C2H5OH    =    H2S04    +     (C2H5)2O. 
Ethyl-sulphuric  Alcohol.  Sulphuric  Ether, 

acid.  acid. 

The  liberated  sulphuric  acid  at  once  attacks  another  molecule  of  alcohol, 
again  forming  ethyl-sulphuric  acid,  which  is  again  decomposed,  etc.  Theo- 
retically, a  given  quantity  of  sulphuric  acid  should  be  capable,  therefore,  of 
converting  any  quantity  of  alcohol  into  ether ;  practically,  however,  this  is  not 
the  case,  because  secondary  reactions  take  place  simultaneously,  and  because 
the  water  «vhich  is  constantly  formed  does  not  all  distil  with  the  ether,  and 
therefore  dilutes  the  acid  to  such  an  extent  that  it  no  longer  acts  upon  the 
alcohol. 

Ether  thus  obtained  is  not  pure,  but  contains  water,  alcohol,  sulphurous  and 
sulphuric  acids,  etc. ;  it  is  purified  by  mixing  it  with  chloride  and  oxide  of 
calcium,  pouring  off  the  clear  liquid  and  distilling  it. 

The  official  ether  contains  of  ethyl-ether  96  per  cent,  and  of 
alcohol  4  per  cent.  It  is  a  very  mobile,  colorless,  highly  volatile 
liquid,  of  a  refreshing,  characteristic  odor,  a  burning  and  sweetish 
taste,  and  a  neutral  reaction  ;  it  is  soluble  in  alcohol,  chloroform, 
liquid  hydrocarbons,  fixed  and  volatile  oils,  and  dissolves  in  ten 
volumes  of  water.  Specific  gravity  is  0.726  at  15° C.  (59°  F.); 
boiling-point  37°  C.  (98.6°  F.).  It  is  easily  combustible  and  burns 
with  a  luminous  flame.  When  inhaled,  it  causes  intoxication  and 
then  loss  of  consciousness  and  sensation.  The  great  volatility  and 
combustibility  of  ether  necessitate  special  care  in  the  handling  of  this 
substance  near  fire  or  light. 


cetheris  and  Spiritus  cetheris  compositus  are  mixtures  of  about  one 
part  of  ether  and  two  parts  of  alcohol,  3  per  cent,  of  certain  ethereal  oils  being 
added  to  the  second  preparation. 


ETHERS.  343 

Acetic  ether,  JEther  aceticus,  C2H5C2H3O2  =  88  (Ethyl  acetate). 
Made  by  mixing  dried  sodium  acetate  with  alcohol  and  sulphuric 
acid,  distilling  and  purifying  the  crude  product  by  shaking  with 
calcium  chloride  and  rectifying  : 

C2H5OH  +  NaC2H302  +  H2SO4  =  C2H5C2H3O2  +  NaHSO4  +  H2O. 
Ethyl  Sodium  Acetic  ether.        Sodium  acid 

alcohol.  acetate.  sulphate. 

Experiment  50.  Add  to  a  mixture  of  40  grammes  of  pure  alcohol  and  100 
grammes  of  concentrated  sulphuric  acid  60  grammes  of  sodium  acetate.  In- 
troduce this  mixture  into  a  boiling-flask,  connect  it  with  a  Liebig's  condenser 
and  distil  about  50  c.  c.  Redistil  the  liquid  from  a  flask,  as  represented  in  Fig. 
39,  page  298,  and  collect  the  portion  which  passes  over  at  a  temperature  of 
IT  C.  (170°  F.) ;  it  is  nearly  pure  ethyl  acetate. 

Acetic  ether  is  a  colorless,  neutral,  and  mobile  liquid,  of  a  strong 
ethereal  and  somewhat  acetous  odor,  soluble  in  alcohol,  ether,  chloro- 
form, etc.,  in  all  proportions,  and  in  17  parts  of  water.  Specific 
gravity  0.894.  Boiling-point  76°  C.  (169°  F.) 

Ethyl  nitrite,  C2H5NO2  (Nitrous  ether).  Made  by  distilling  a  mix- 
ture of  alcohol,  sulphuric  acid,  and  sodium  nitrite  : 

C2H5OH  +  NaN02  +  H2SO4  =  C2H5NO2  +  NaHSO4  +  H2O 

The  distillate,  which  contains,  besides  ethyl  nitrite,  some  alcohol 
and  often  some  decomposition  products,  is  washed  with  ice-cold  water, 
in  which  ethyl  nitrite  is  nearly  insoluble,  and  with  sodium  carbonate 
to  remove  traces  of  acid  ;  finally,  it  is  freed  from  water  by  treatment 
with  anhydrous  potassium  carbonate. 

Spirit  of  nitrous  ether,  Spiritus  cetheris  nitrosi,  Sweet  spirit  of  nitre. 

This  is  a  mixture  of  about  4  parts  of  ethyl  nitrite  with  96  parts 
of  alcohol.  It  is  a  clear,  mobile,  volatile,  and  inflammable  liquid,  of 
a  pale  straw  color  inclining  slightly  to  green,  a  fragrant,  ethereal 
odor,  and  a  sharp,  burning  taste.  It  is  neutral,  or  but  very  slightly 
acid  to  litmus  paper  but  evolves  no  carbon  dioxide  with  potassium 
bicarbonate. 

Amyl  nitrite,  Amyl  nitris,  C5HUNO2  =  117.  Made  by  a  process 
analogous  to  the  one  mentioned  above  for  ethyl  nitrite,  substituting 
amyl  alcohol  for  ethyl  alcohol. 

The  official  amyl  nitrite  contains  of  this  ether  about  80  per  cent, 
together  with  variable  quantities  of  undetermined  compounds;  it 
is  a  clear,  pale-yellowish  liquid,  of  an  ethereal,  fruity  odor,  an 
aromatic  taste,  and  a  neutral  or  slightly  acid  reaction.  Specific 
gravity  0.872.  Boiling-point  96°  C.  (205°  F.). 


344  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Fats  and  fat  oils.  All  true  fats  are  compound  ethers  of  the  tri- 
atomic  alcohol  glycerin,  in  which  the  three  replaceable  hydrogen  atoms 
of  the  hydroxyl  are  replaced  by  three  univalent  radicals  of  the  higher 
members  of  the  fatty  acids.  For  instance : 

OH 

Glycerin  =  C3H5.(OH)3  or  C3H5rlOH 

\OH 
Stearicacid  =  C18H35O.OH  or  C18H35O\O 

H/ 

(C18H35O).0 

Stearin  or  tristearin  =  C3H5.(C18H35O)3.O3  or  C3H5:_ (C18H35O).O 

\(C18H350).0 

While  all  natural  fats  are  glycerin  in  which  the  three  hydrogen 
atoms  are  replaced,  we  may  by  artificial  means  introduce  but  one  or 
two  acid  radicals,  thus  forming : 

(C18H350)0  (C18H350)0 

Monostearin  =  C3H5_OH  Distearin  =  C3H5^_(C18H35O)O 

\OH  \(OH) 

Fats  are  often  termed  glycerides ;  stearin  being,  for  instance,  the 
glyceride  of  stearic  acid. 

The  principal  fats  consist  of  mixtures  of  palmitin,  C3H5.(C16H31O)3. 
O,,  stearin,  C3H6.(C18H35O)3.O3,  and  olein,  C3H5.(C18H33O)3.O3. 
Stearin  and  palmitin  are  solids,  olein  is  a  liquid  at  ordinary  tem- 
perature ;  the  relative  quantity  of  the  three  fats  mentioned  determines 
its  solid  or  liquid  condition.  The  liquid  fats,  containing  generally 
olein  as  their  chief  constituent,  are  called  fatty  oils  or  fixed  oils  in 
contradistinction  to  volatile  or  essential  oils. 

All  fats,  when  in  a  pure  state,  are  colorless,  odorless,  and  tasteless 
substances,  which  stain  paper  permanently  ;  they  are  insoluble  in 
water,  difficultly  soluble  in  cold  alcohol,  easily  soluble  in  ether,  disul- 
phide  of  carbon,  benzene,  etc.  The  taste  and  color  of  fats  are  due  to 
foreign  substances,  often  produced  by  a  slight  decomposition  which 
has  taken  place  in  some  of  the  fat.  All  fats  are  lighter  than  water, 
and  all  solid  fats  fuse  below  100°  C.  (212°  F.) ;  fats  can  be  distilled 
without  change  at  about  300°  C.  (572°  F.),  but  are  decomposed  at  a 
higher  temperature  with  the  formation  of  numerous  products,  some 
of  which  have  an  extremely  disagreeable  odor,  as,  for  instance, 
acrolein,  C3H4O,  an  aldehyde  which  in  composition  is  equal  to 
glycerin  minus  two  molecules  of  water  : 

C3H5(HO)3    -  -    2H20    =    C3H40. 

Some  fats  keep  without  change  when  pure ;  since  they  contain, 
however,  impurities  generally,  such  as  albuminous  matter,  etc.,  they 


ETHERS.  345 

suffer  decomposition  (a  kind  of  fermentation  aided  by  oxidation), 
which  results  in  a  liberation  of  the  fatty  acids,  which  impart  their 
odor  and  taste  to  the  fats,  causing  them  to  become  what  is  generally 
termed  rancid. 

Some  fats,  especially  some  oils,  suffer  oxidation,  which  renders 
them  hard.  These  drying  oils  differ  from  other  oils  in  being  mixtures 
of  olein  with  another  class  of  glycerides,  containing  unsaturated  acids 
with  less  hydrogen  in  relation  to  carbon  than  oleic  acid.  Drying  oils 
are  prevented  from  drying  by  albuminous  impurities,  which  may  be 
removed  by  treating  the  oil  with  4  per  cent  of  concentrated  sulphuric 
acid  ;  the  acid  does  not  act  on  the  fat,  but  quickly  destroys  the  albu- 
minous matters,  which,  with  the  sulphuric  acid,  sink  to  the  bottom, 
whilst  the  "  refined  "  oil  may  be  removed  by  decantation. 

Fats  are  largely  distributed  in  the  animal  and  vegetable  kingdoms. 
They  exist  in  plants  chiefly  in  the  seeds,  while  in  animals  they  are 
found  generally  under  the  skin,  around  the  intestines,  and  on  the 
muscles. 

Human  fat,  beef  tallow,  mutton  tallow,  and  lard  are  mixtures  of 
palmitin  and  stearin  with  some  olein.  Butter  consists  of  the  glycer- 
ides of  butyric  acid,  capro'ic  acid,  caprylic  acid,  and  capric  acid, 
which  are  volatile  with  water  vapors,  and  of  myristic,  palmitic,  and 
stearic  acids,  which  are  not  volatile. 

The  principal  non-drying  vegetable  oils  (consisting  chiefly  of  olein) 
are  olive  oil,  cottonseed  oil,  cocoanut  oil,  palm  oil,  almond  oil. 

Among  the  drying  oils  are  of  importance  :  linseed  oil,  castor  oil, 
croton  oil,  hemp  oil,  cod-liver  oil. 

Whenever  fats  are  treated  with  alkaline  hydroxides,  or  with  a 
number  of  other  metallic  oxides,  decomposition  takes  place,  the  fatty 
acids  combining  with  the  metals,  whilst  glycerin  is  set  free.  Some 
of  the  substances  thus  formed  are  of  great  importance,  as,  for  instance, 
the  various  kinds  of  soap. 

Soap.  Any  fat  boiled  with  sodium  or  potassium  hydroxide  will 
form  soap.  Soft  soap  is  potassium  soap,  hard  soap  is  sodium  soap. 
The  better  kinds  of  hard  soap  are  made  by  boiling  olive  oil  with 
sodium  hydroxide  : 


18H3302)3  +  3NaOH  =  3NaC18H33O,  +  C3H5(OH)3. 
Oleateof  glyceryl  Sodium  Sodium  oleate  Glycerin. 

(olive  oil).  hydroxide.          (hard  soap). 

Experiment  51.  Boil  50  grammes  of  olive  oil  with  60  c.c.  of  a  15  per  cent. 
sodium  hydroxide  solution  for  about  one  hour.  The  soap  which  is  thereby 
formed  remains  dissolved  in  or  mixed  with  water  and  glycerin.  Cause  sepa- 
ration by  adding  a  solution  of  15  grammes  of  sodium  chloride  in  40  c.c.  of 


346  CONSIDERATION  OF  CARBON  COMPOUNDS. 

water  and  boiling  for  a  short  while,  when  the  soap,  which  is  insoluble  in  the 
salt  solution,  rises  to  the  surface  and  solidifies  on  cooling. 

Soaps  are  soluble  in  water  and  alcohol ;  they  contain  rarely  less  than 
30  per  cent.,  but  sometimes  as  much  as  70-80  per  cent,  of  water. 

Ammonia  liniment,  Linimentum  ammonice,  and  lime  liniment,  Lini- 
mentum  colds,  are  obtained  by  mixing  cottonseed  oil  with  water  of 
ammonia  and  lime-water,  respectively.  The  oleate  of  ammonium  or 
calcium  is  formed,  and  remains  mixed  with  the  liberated  glycerin. 

Lead  plaster,  Emplastrum  plumbi.  Chiefly  lead  oleate,  Pb(C18H33O2)2. 
Obtained  by  boiling  lead  oxide  with  olive  oil  and  water  for  several 
hours,  until  a  homogeneous,  pliable,  and  tenacious  mass  is  formed. 
Lead  oleate  differs  from  the  oleates  of  the  alkalies  by  its  complete 
insolubility  in  water. 

Wool-fat,  Lanolin.  This  is  the  fat,  or  a  mixture  of  fats,  found  in  sheep's 
wool  and  obtained  by  treating  the  wool  with  soap-water,  and  acidifying  the 
wash  liquor,  when  the  fats  separate  unchanged.  These  fats  differ  from  the  fats 
spoken  of  above  in  so  far  as  the  alcohol  present  is  not  glycerin,  but  an  alcohol, 
or  rather  two  isomeric  alcohols  of  the  composition  C26H43OH  and  known  as 
cholesterin  and  iso-cholesterin.  These  alcohols,  which  are  white,  crystalline, 
fusible  substances,  when  in  combination  with  fatty  acids  form  the  compound 
ethers  known  as  lanolin. 

Lanolin  is  a  yellowish-white  (or,  when  not  sufficiently  purified,  a  more  or 
less  brownish),  fat-like  substance,  having  the  peculiar  odor  of  sheep's  wool  and 
fusing  at  about  40°  C.  (104°  F.),  forming  an  oily  liquid.  Unlike  true  fats, 
lanolin  is  capable  of  mixing  with  twice  its  weight  of  water  or  aqueous  solutions 
and  yet  retaining  its  fatty  consistency ;  it  is,  moreover,  much  less  liable  to  de- 
compose than  fats,  and  it  is  this  property  and  its  power  to  mix  with  aqueous 
solutions  which  have  rendered  lanolin  a  valuable  agent  in  certain  pharma- 
ceutical preparations.  Official  is  hydrous  wool-fat,  the  purified  fat  mixed  with 
not  more  than  30  per  cent,  of  water. 

QUESTIONS  — 441.  Explain  the  constitution  of  simple,  mixed,  and  compound 
ethers.  To  what  inorganic  compounds  are  they  analogous?  442.  State  the 
general  processes  for  the  formation  of  ethers  and  compound  ethers.  443. 
What  is  the  composition  of  ethyl  ether?  Explain  the  process  of  its  manufac- 
ture in  words  and  symbols,  and  state  its  properties.  444.  How  is  acetic  ether 
made,  and  what  are  its  properties?  445.  What  is  sweet  spirit  of  nitre,  and 
how  is  it  made  ?  446.  State  the  general  composition  of  fats  and  he  chief  con- 
stituents of  tallow,  butter,  and  olive  oil.  447.  What  is  the  soli  oility  of  fats 
in  water,  alcohol,  and  ether ;  how  do  heat  and  oxygen  act  upon  hem ;  what 
is  the  cause  of  their  becoming  rancid?  448.  Explain  the  composition  and 
manufacture  of  soap,  and  state  the  difference  between  hard  and  soft  soap. 
449.  How  are  ammonia  liniment,  lime  liniment,  and  lead  plaster  made,  and 
what  is  their  composition  ?  450.  What  is  the  source  of  lanolin ;  what  are  its 
constituents  and  properties  ? 


CARBOHYDRATES.  347 


46.    CARBOHYDRATES. 

Constitution.  The  term  carbohydrates  or  carbhydrates  is  not 
well  chosen,  because  it  implies  that  these  substances  are  carbon  in 
combination  with  water.  Carbohydrates  do  contain  hydrogen  and 
oxygen  in  the  proportion  of  two  atoms  of  hydrogen  to  one  atom  of 
oxygen,  or  in  the  proportion  to  form  water,  but  this  does  not  exist  as 
such  in  the  carbohydrates. 

The  true  atomic  structure  of  carbohydrates  is  as  yet  but  little 
known.  The  compounds  of  the  composition  C6H12O6  are  now  looked 
upon  as  the  aldehyde  of  the  hexatomic  alcohol  mannite,  C6H14O6,  the 
chief  constituent  of  manna  : 

C6HU06    -       2H       :    C6H1206. 

Mannite  itself  is  formed  from  the  saturated  hydrocarbon  C6H14, 
by  replacement  of  6  atoms  of  hydrogen  by  6OH ;  its  constitutional 
formula  is,  therefore,  (C6H8)vi.(OH)6. 

Carbohydrates  generally  contain  6  atoms  of  carbon  or  a  multiple 
of  6. 

Properties.  Carbohydrates  are  either  fermentable,  or  can,  in  most 
cases,  be  converted  into  substances  which  are  capable  of  fermentation. 
They  are  not  volatile,  but  suffer  decomposition  when  sufficiently 
heated  ;  they  have  neither  acid  nor  basic  properties,  but  are  of  a  neu- 
tral reaction.  Oxidizing  agents  convert  them  into  saccharic  and 
mucic  acids  and  finally  into  oxalic  acid.  (Soluble  carbohydrates 
have  the  property  of  bending  the  plane  of  polarized  light.) 

Most  carbohydrates  are  white,  solid  substances,  and,  with  the  ex- 
ception of  a  few,  soluble  in  water.  The  members  of  the  first  two 
groups  (glucoses  and  saccharoses)  have  a  more  or  less  sweet  taste. 
Many  of  them,  especially  glucoses,  are  good  reducing  agents,  as  is 
shown  by  the  fact  that  they  deoxidize  in  alkaline  solution  salts  (or 
oxides)  of  copper,  bismuth,  mercury,  gold,  etc.,  either  to  a  lower  state 
of  oxidation  or  to  the  metallic  state. 

Occurrence  in  nature.  No  other  organic  substances  are  found  in 
such  immense  quantities  in  the  vegetable  kingdom  as  the  members 
of  this  group,  cellulose  being  a  chief  constituent  of  all,  starch  and 
various  kinds  of  sugar  of  most  plants.  Carbohydrates  are  also  found 
as  products  of  animal  life,  as,  for  instance,  the  sugar  in  milk,  in  bees' 
honey,  etc. 


348  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Groups  of  carbohydrates. 


Glucoses. 
C6H1206. 
"  Grape-sugar, 
Fruit-sugar, 
Mannitose, 

Saccharoses. 
C12H22On  . 
Cane-sugar, 
Melitose, 
Maltose, 

Amyloses. 
C6H1005. 
Starch, 
Dextrin, 
Gums, 
Cellulose, 

Inosite. 

Milk-sugar. 

Glycogen. 

Origin  |     Vegetable 

Animal 

Grape-sugar,  C6H12O6  (Ordinary  glucose,  Dextrose).  This  sub- 
stance is  very  abundantly  diffused  throughout  the  vegetable  kingdom, 
and  is  generally  accompanied  by  fruit-sugar.  It  is  contained  in 
large  quantities  in  the  juice  of  many  fruits  ;  the  percentage  of  grape- 
sugar  in  the  dried  fig  is  about  65,  in  grape  10-20,  in  cherry  11,  in 
mulberry  9,  in  strawberry  6,  etc. 

Grape-sugar  is  found  also  in  honey  and  in  minute  quantities  in  the 
normal  blood  (0.1  per  cent,  or  less),  and  traces  occur,  perhaps,  in 
normal  urine,  the  quantity  in  both  liquids  rising,  however,  during 
certain  diseases,  as  high  as  '5  per  cent,  or  higher. 

Grape-sugar  is  produced  in  the  plant  from  starch  by  the  action  of 
the  vegetable  acids  present;  it  may  be  obtained  artificially  from 
starch  (and  from  many  other  carbohydrates)  by  heating  with  dilute 
mineral  (sulphuric)  acids,  which  convert  starch  first  into  dextrin  and 
then  into  grape-sugar.  Corn-starch  is  now  largely  used  for  that  pur- 
pose, the  excess  of  sulphuric  acid  being  removed  by  treating  the  solu- 
tion with  chalk ;  the  filtered  solution  is  either  evaporated  to  a  syrup 
and  sold  as  "glucose,"  or 'evaporated  to  dryness,  when  the  com- 
mercial "  grape-sugar  "  is  obtained. 

Experiment  52.  Heat  to  boiling  100  c.c.  of  a  1  per  cent,  sulphuric  acid  and 
add  to  it  very  gradually  and  under  constant  stirring  a  mixture  made  by  rub- 
bing together  25  grammes  of  starch  and  25  grammes  of  water.  Continue  to  boil 
until  iodine  no  longer  causes  a  blue  color  (which  shows  complete  conversion  of 
starch  into  either  dextrin  or  glucose),  and  until  1  c.c.  of  the  solution  is  no  longer 
precipitated  on  the  addition  of  6  c.c.  of  alcohol  (which  shows  the  conversion  of 
dextrin  into  sugar,  dextrin  being  precipitated  by  alcohol).  Apply  to  a  portion 
of  the  glucose  solution  thus  obtained,  and  neutralized  by  sodium  carbonate,  the 
tests  mentioned  below.  To  the  remaining  solution  add  a  quantity  of  precipitated 
calcium  carbonate  sufficient  to  convert  all  sulphuric  acid  into  calcium  sulphate. 
Filter,  evaporate  the  solution  to  a  syrup  and  notice  its  sweet  taste. 

Glucose  is  met  with  generally  as  a  thick  syrup  which  crystallizes 
with  difficulty,  combining  during  crystallization  with  one  molecule  of 
water;  but  anhydrous  crystals,  closely  resembling  those  of  cane- 
sugar,  are  also  known.  Glucose  is  soluble  in  its  own  weight  of 


CARBOHYDRATES.  349 

water  and  is  less  sweet  than  cane-sugar,  the  sweetness  of  glucose  com- 
pared to  that  of  cane-sugar  being  about  3  to  5  ;  when  heated  to  170° 
C.  (338°  F.)  it  loses  water,  and  is  converted  into  glucosan,  C6H10O5 ; 
by  stronger  heating  it  loses  more  water  and  forms  caramel,  a  mixture 
of  various  substances ;  it  turns  the  plane  of  polarized  light  to  the 
right. 

Grape-sugar  combines  with  various  metallic  oxides  (alkalies,  alka- 
line earths,  etc.),  and  also  with  a  number  of  other  substances,  form- 
ing a  series  of  compounds  known  as  glucosides. 

Grape-sugar  may  be  recognized  analytically : 

1.  By  causing  a  bright-red  precipitate  of  cuprous  oxide,  when 
boiled  with  a  solution  of  cupric  sulphate  in  sodium  hydroxide,  to 
which  tartaric  acid  has  been  added.     (A  solution  containing  these 
three  substances  in  definite  proportions  is  known  as  Fehling's  solu- 
tion.    See  index.) 

2.  By  precipitating  metallic  silver,  bismuth,  and  mercury,  when 
compounds  of  these  metals  are  heated  with  it  in  the  presence  of 
caustic  alkalies. 

3.  By  easily  fermenting  when   yeast   is  added  to  the  solution, 
alcohol  and  carbon  dioxide  being  formed : 

C6H1206    :   :    2C2H5OH    +     2C02. 

Fruit-sugar,  C6H12O6  (Levulose),  occurs  with  glucose  in  sweet 
fruits  and  honey ;  it  resembles  glucose  in  most  chemical  and  physical 
properties,  but  does  not  crystallize  from  an  aqueous  solution ;  it  may, 
however,  be  obtained  in  white,  silky  needles  from  an  alcoholic  solu- 
tion ;  it  is  met  with  generally  as  a  thick  syrup,  is  about  as  sweet  as 
cane-sugar,  and  turns  the  plane  of  polarized  light  to  the  left;  it  is 
formed  by  the  action  of  dilute  mineral  acids  or  ferments  on  cane- 
sugar,  which  latter  takes  up  water  and  breaks  up  thus : 

C12H22On    +    H20    :   .    C6H1206    +     C6H1206. 
Cane-sugar.  Dextrose.  Levulose. 

Mannitose,  C6H12O6.  Obtained  by  the  oxidation  of  mannite;  it 
does  not  crystallize  and  resembles  grape-sugar. 

Galactose,  C6H12O6,  is  formed  together  with  dextrose  when  either 
milk-sugar  or  gum-arabic  is  boiled  with  dilute  sulphuric  acid.  Galac- 
tose  crystallizes,  reduces  an  alkaline  copper  solution,  but  does  not 
ferment  with  yeast. 

Inosite,  CbH12O6  (Muscle-sugar),  occurs  in  various  muscular  tissues, 
in  the  lungs,  kidneys,  liver,  spleen,  brain,  and  blood.  Although 


350  CONSIDERATION  OF  CARBON  COMPOUNDS. 

identical  in  composition  with  grape-sugar,  inosite  differs  from  the 
latter  in  not  being  fermentable  and  by  not  precipitating  cuprous 
oxide  from  alkaline  copper-solutions. 

Cane-sugar,  Saccharum,  C12H22OU  =  342  (Ordinary  saccharose, 
Common  sugar,  Beet-sugar).  Cane-sugar  is  found  in  the  juices  of 
many  plants,  especially  in  that  of  the  different  grasses  (sugar-cane), 
and  also  in  the  sap  of  several  forest  trees  (maple),  in  the  roots,  stems, 
and  other  parts  of  various  plants  (sugar-beet),  etc.  Plants  contain- 
ing cane-sugar  do  not  contain  free  organic  acids,  which  latter  would 
convert  it  into  grape-sugar. 

Cane-sugar  is  manufactured  from  various  plants  containing  it  by 
crushing  them  between  rollers,  expressing  the  juice,  heating  and 
adding  to  it  milk  of  lime,  which  precipitates  vegetable  albuminous 
matter.  The  clear  liquid  is  evaporated  to  the  consistency  of  a  syrup, 
which  is  further  purified  (refined)  by  filtering  it  through  bone-black 
and  evaporating  the  solution  in  "  vacuum  pans"  to  the  crystallizing- 
point;  the  mother-liquors  are  further  evaporated,  and  yield  lower 
grades  of  sugar ;  finally  a  syrup  is  left  which  is  known  as  molasses. 

Cane-sugar  forms  white,  hard,  distinctly  crystalline  granules,  but 
may  be  obtained  also  in  well-formed,  large,  monocliuic  prisms.  It 
dissolves  in  0.2  part  of  boiling,  in  0.5  part  of  cold  water,  and  in  175 
parts  of  alcohol ;  when  heated  to  160°  C.  (320°  F.)  it  fuses,  and  the 
liquid,  on  cooling,  forms  an  amorphous,  transparent  mass,  known  as 
barley  sugar;  at  a  higher  temperature  cane  sugar  is  decomposed, 
water  is  evolved,  and  a  brown,  almost  tasteless  substance  is  formed, 
which  is  known  as  caramel  or  burnt  sugar.  Oxidizing  agents  act 
energetically  upon  cane-sugar,  which  is  a  strong  reducing  agent.  A 
mixture  of  cane-sugar  and  potassium  chlorate  will  deflagrate  when 
moistened  with  sulphuric  acid;  potassium  permanganate  is  readily 
deoxidized  in  acid  solution ;  cane-sugar,  however,  does  not  affect  an 
alkaline  copper-solution,  and  does  not  ferment  itself;  but  when  heated 
with  dilute  acids  or  left  in  contact  with  yeast  for  some  time,  it  is 
decomposed  into  dextrose  and  levulose,  both  of  which  are  ferment- 
able. Like  dextrose,  cane-sugar  forms  compounds  with  metals, 
metallic  oxides,  and  salts,  which  compounds  are  known  as  sucrates. 

Experiment  53.  Make  a  one  per  cent,  cane-sugar  solution ;  test  it  with 
Fehling's  solution  and  notice  that  no  cuprous  oxide  is  precipitated.  Add  to 
50  c  c.  of  the  cane-sugar  solution  5  drops  of  hydrochloric  acid  and  heat  on  a 
water-bath  for  half  an  hour.  Again  examine  the  liquid  with  Fehling's  solu- 
tion ;  a  precipitate  of  cuprous  oxide  is  now  formed,  proving  the  conversion  of 
cane-sugar  into  glucose. 


CARBOHYDRATES.  351 

Maltose,  O12H22OU,  is  obtained  by  the  action  of  diastase  on  starch. 
Diastase  is  a  substance  formed  during  the  germination  of  various 
seeds  (rye,  wheat,  barley,  etc.),  and  it  is  for  this  reason  that  grain 
used  for  alcoholic  liquors  is  allowed  to  germinate,  during  which  pro- 
cess diastase  is  formed,  which,  acting  upon  the  starch  present,  con- 
verts it  into  maltose  and  dextrin: 

3(C6H1005)     +    H20       :    C12H22On     +    C6H1005. 
Starch.  Maltose.  Dextrin. 

Maltose  is  also  formed  by  the  action  of  dilute  sulphuric  acid  upon 
starch,  and  is  hence  often  present  in  commercial  glucose;  by  further 
treatment  with  sulphuric  acid  it  is  converted  into  dextrose.  Maltose 
crystallizes,  reduces  alkaline  copper  solutions,  and  ferments  with 
yeast. 

Melitose,  C12H22OU,  is  the  chief  constituent  of  Australian  manna. 

Milk-sugar,  Saccharum  lactis,  C12H22On+  H2O  ===  36O  (Lactose). 
Found  almost  exclusively  in  the  milk  of  the  mammalia.  Obtained 
by  freeing  milk  from  casein  aud  fat  and  evaporating  the  remaining 
liquid  (whey)  to  a  small  bulk,  when  the  milk-sugar  crystallizes  on 
cooling. 

It  forms  white,  hard,  crystalline  masses ;  it  is  soluble  in  about  6 
parts  of  water  (at  15°  C.,  59°  F.)  and  in  1  part  of  boiling  water, 
insoluble  in  alcohol  and  ether;  it  is  much  harder  than  cane-sugar, 
and  but  faintly  sweet ;  it  is  not  easily  brought  into  alcoholic  fermen- 
tation by  the  action  of  yeast,  but  easily  undergoes  "  lactic  fermenta- 
tion" when  cheese  is  added.  During  this  process  milk-sugar  i& 
converted  into  lactic  acid. 

Milk-sugar  resembles  grape-sugar  in  its  action  on  alkaline  solution 
of  copper,  from  which  it  precipitates  cuprous  oxide. 

Starch,  Amylum,  C6H10O5  =  162.  Starch  is  very  widely  dis- 
tributed in  the  vegetable  kingdom,  and  is  found  chiefly  in  the  seeds 
of  cereals  and  leguminosse,  but  also  in  the  roots,  stems,  and  seeds  of 
nearly  all  plants. 

It  is  prepared  from  wheat,  potatoes,  rice,  beans,  sago,  arrow-root, 
etc.,  by  a  mechanical  operation.  The  vegetable  matter  containing 
the  starch  is  comminuted  by  rasping  or  grinding,  in  order  to  open 
the  cells  in  which  it  is  deposited,  and  then  steeped  in  water;  the 
softened  mass  is  then  rubbed  on  a  sieve  under  a  current  of  water 
which  washes  out  the  starch,  while  cellular  fibrous  matter  remains  on 


352  CONSIDERATION  OF  CARBON  COMPOUNDS. 

the  sieve;  the  starch  deposits  slowly  from  the  washings,  and  is 
further  purified  by  treating  it  with  water. 

Starch  forms  white,  amorphous,  tasteless  masses,  which  are  pecu- 
liarly slippery  to  the  touch,  and  easily  converted  into  a  powder;  it 
is  insoluble  in  cold  wrater,  alcohol,  and  ether;  when  boiled  with  water, 
it  yields  a  white  jelly  (mucilage  of  starch,  starch-paste)  which  cannot 
be  looked  upon  as  a  true  solution,  but  is  a  suspension  of  the  swollen 
starch  particles  in  water ;  by  continued  boiling  with  much  water  some 
starch  passes  into  solution. 

Starch,  when  examined  under  the  microscope,  is  seen  to  consist  of 
granules  differing  in  size,  shape,  and  appearance,  according  to  the 
plant  from  which  the  starch  was  obtained.  Concentric  layers,  which 
are  more  or  less  characteristic  of  starch-granules,  show  that  they  are 
formed  in  the  plant  by  a  gradual  deposition  of  starch  matter. 

The  most  characteristic  test  for  starch  is  the  dark-blue  color  which 
iodine  imparts  to  it  (or  better  to  the  mucilage).  This  color  is  due  to 
the  formation  of  iodized  starch,  an  unstable  dark-blue  compound  of 
the  doubtful  composition  C6H9IO5I. 

Starch  is  an  important  article  of  food,  especially  when  associated, 
as  in  ordinary  flour,  with  albuminous  substances. 

Dextrin,  C6H10O5  (British  gum).  Obtained  by  boiling  starch  with 
diluted  acids,  or  by  subjecting  starch  to  a  dry  heat  of  175°  C. 
(347  °-F.)  or  by  the  action  of  diastase  (infusion  of  malt)  upon 
hydrated  starch.  Malt  is  made  by  steeping  barley  in  water  until  it 
germinates,  and  then  drying  it. 

Dextrin  is  a  colorless  or  slightly  yellowish,  amorphous  powder, 
resembling  gum-arabic  in  some  respects;  it  is  soluble  in  water,  re- 
duces alkaline  copper  solutions,  and  is  colored  light  wine-red  by 
iodine.  It  is  extensively  used  in  mucilage  as  a  substitute  for  gum- 
arabic. 

Gums.  These  are  amorphous  substances  of  vegetable  origin, 
soluble  in  water  or  swelling  up  in  it,  forming  thick,  sticky  masses ; 
they  are  insoluble  in  alcohol,  and  are  converted  into  glucose  by  boil- 
ing with  dilute  sulphuric  acid.  Some  gums  belong  to  the  saccharoses, 
others  to  the  amyloses. 

Acacia,  Gum-arabic  is  a  gummy  exudation  from  Acacia  Senegal ; 
it  consists  chiefly  of  the  calcium  salt  of  arabic  acid,  C12H22On.  Other 
gums  occur  in  the  cherry  tree,  in  linseed  or  flaxseed,  in  Irish  moss, 
in  marsh-mallow  root,  etc. 


CARBOHYDRATES.  353 

Gum-arabic  dissolves  slowly  in  2  parts  of  water ;  this  solution 
shows  an  acid  reaction  with  litmus,  and  yields  precipitates  with  lead 
acetate  or  ferric  chloride. 

Cellulose,  C6H10O5,  perhaps  C18H30O15  (Plant  fibre,  Lignine).  Cellu- 
lose constitutes  the  fundamental  material  of  which  the  cellular  mem- 
brane of  vegetables  is  built  up,  and  forms,  therefore,  the  largest 
portion  of  the  solid  parts  of  every  plant;  it  is  well  adapted  to  this 
purpose  on  account  of  its  insolubility  in  water  and  most  other  sol- 
vents, its  resistance  to  either  alkaline  or  acid  liquids,  and  its  tough 
and  flexible  nature.  Some  parts  of  vegetables  (cotton,  hemp,  and 
flax,  for  instance)  are  nearly  pure  cellulose. 

Pure  cellulose  is  a  white,  translucent  mass,  insoluble  in  all  the 
common  solvents,  but  soluble  in  an  ammoniacal  solution  of  basic 
cupric  carbonate ;  it  is  not  colored  blue  by  iodine. 

Treated  with  concentrated  sulphuric  acid  it  swells  up,  and  gradu- 
ally dissolves ;  water  precipitates  from  such  solutions  a  substance 
known  as  amyloid,  which  is  an  altered  cellulose  giving  a  blue  color 
with  iodine.  Upon  diluting  the  sulphuric  acid  solution  with  water 
and  boiling  it,  the  cellulose  is  gradually  converted  into  dextrin  and 
dextrose. 

Unsized  paper  (which  is  chiefly  cellulose)  dipped  into  a  mixture 
of  two  volumes  of  sulphuric  acid  and  one  volume  of  water,  forms, 
after  being  washed  and  dried,  the  so-called  "  parchment  paper," 
which  possesses  all  the  valuable  properties  of  parchment. 

Pyroxylin,  Pyroxylinum,  C6H8O3(NO3)2  (  Cellulose  dinitrate,  Sol- 
uble gun-cotton,  Nitro-cellulose).  By  the  action  of  nitric  acid  of 
various  strengths  on  cellulose,  three  different  substitution  products 
(possibly  compound  ethers)  may  be  obtained,  which  are  distinguished 
as  cellulose  mono-,  di-,  and  trinitrate  : 

C6H1005    +      HN03    =      H20    +     C6H904N03. 
C6H1005    +     2HN03    =    2H20    +     C6H8O3(NO3)2 
C6H1005    +    3HN03    t=    3H20    +    C6H7O2(NO3)3. 

Cellulose  trinitrate  is  the  highly  explosive  gun-cotton  ;  an  intimate 
mixture  of  gun-cotton  and  camphor  is  now  extensively  used  under 
the  name  of  celluloid.  Cellulose  dinitrate  or  pyroxylin  is  soluble  in 
a  mixture  of  ether  and  alcohol ;  this  solution  is  known  as  collodion. 

Experiment  54.  Immerse  2  grammes  of  dry  cotton  for  ten  hours  in  a  pre- 
viously cooled  mixture  of  28  c.c.  of  nitric  acid  and  44  c.c.  of  sulphuric  acid. 
Wash  the  pyroxylin  thus  obtained  with  cold  water  until  the  washings  have  no 

23 


354  CONSIDERATION  OF  CARBON  COMPOUNDS. 

longer  an  acid  reaction.     Dissolve  1  gramme  of  the  dry  pyroxylin  in  a  mixture 
of  25  c.c.  of  ether  and  8  c.c.  of  alcohol.     The  solution  obtained  is  collodion. 

Gly  cog-en,  C6H10O5.  Found  exclusively  in  animals  ;  it  occurs  in 
the  liver,  the  white  blood-corpuscles,  in  many  embryonic  tissues,  and 
in  muscular  tissue.  Pure  glycogen  is  a  white,  starch-like,  amorphous 
substance,  soluble  in  water,  insoluble  in  alcohol ;  by  the  action  of 
dilute  acids  it  is  converted  into  glucose. 

Glucosides.  This  term  is  applied  to  a  group  of  substances  (chiefly 
of  vegetable  origin)  which,  by  the  action  of  acids,  alkalies,  or  fer- 
ments, suffer  decomposition  in  such  a  manner  that  one  of  the  products 
formed  is  grape-sugar.  Glucosides  may,  therefore,  be  looked  upon 
as  compound  sugars,  or  sugar  in  combination  with  various  other  sub- 
stances. The  following  is  a  list  of  the  more  important  glucosides, 
giving  also  their  composition  and  the  sources  whence  they  are 
obtained : 

Amygdalin,  C20H2rNOn  Bitter  almonds,  etc 

Cathartic  acid,  C180H19,N4SO82?  Senna. 

Carminic  acid,  C17H18O10  Cochineal. 

Colocynthin,  C58H84O23?  Colocynthis. 

Digitalin,  ?  Digitalis 

Gentiopicrin,  C30H30O12  Root  of  gentiana. 

Glycyrrhizin,  C24H36O9  Liquorice  root. 

.    Helleborin,  C36H42O6  Root  of  hellebore. 

Indican,  C26H31NO17  Indigo  plant. 

Myronic  acid,  C10H19NS2O10  Seeds  of  black  mustard. 

Salicin,  C13H18O7  Bark  of  willow. 

Tannins,  CUH10O9  In  many  barks,  leaves,  etc. 

Digitalin.  The  leaves  of  digitalis  purpurea  contain  a  number  of  glucosides, 
mixtures  of  which  in  varying  proportions  form  the  official  article  sold  under 
above  name.  Digitonin  is  an  amorphous,  yellowish  substance,  soluble  in 
alcohol.  Digitalein  is  a  white,  intensely  bitter,  amorphous  substance.  Digi- 
toxin  is  a  colorless,  crystalline  solid ;  it  is  the  most  poisonous  of  the  constituents 
of  digitalin,  and  is  found  in  the  leaves  only  to  the  extent  of  0.01  to  0.02  per 
cent. ;  it  is  not  a  glucoside.  Digitalin,  (C5H8O2)#,  is  a  white  amorphous  powder, 
soluble  at  ordinary  temperature  in  about  1000  parts  of  water  and  in  about  100 
parts  of  alcohol  of  50  per  cent.  It  is  soluble  in  concentrated  hydrochloric 
acid,  forming  a  golden  yellow  solution.  A  similar  yellow  solution  is  obtained 
by  dissolving  it  in  concentrated  sulphuric  acid,  the  color  gradually  changing 
to  blood-red.  The  yellow  color  of  the  sulphuric  acid  solution  changes  to  a 
beautiful  violet  on  the  addition  of  a  drop  of  nitric  acid  or  ferric  chloride. 

Myronic  acid,  C10H19NS2010,  is  found  as  the  potassium  salt,  which  is  known 
as  sinigrin,  in  black  mustard  seed.  When  treated  with  solution  of  myrosin,  a 
substance  also  contained  in  mustard  seed  and  acting  as  a  ferment  upon  myronic 


AMINES  AND  AMIDES.     CYANOGEN  COMPOUNDS.  355 

acid  or  its  salts,  potassium  myronate  is  converted  into  dextrose,  allyl  mustard 
oil,  and  potassium  bisulphate : 

KC10H]8N82010  =  C6H1206  +  C3H5NCS  +  KHSO4. 
Potassium  Dextrose.      Allyl  mustard      Potassium 

myronate.  oil.  bisulphate. 

The  univalent  radical  allyl,  C3H5!,  is  isomeric,  but  not  identical  with  the 
trivalent  radical  glyceryl,  C3H5Ui.  The  triatomic  alcohol  glycerin,  C3H5(OH)3, 
may,  however,  be  converted  into  the  monatomic  allyl  alcohol  C3H5OH,  by 
various  processes.  From  allyl  alcohol  an  artificial  allyl  mustard  oil  is  manu- 
factured. 

Allyl  sulphide,  (C3H5)2S,  is  the  chief  constituent  of  the  oil  of  garlic. 

Elaterin,  C20H2805.  Obtained  from  the  fruit  of  Ecballium  elaterium.  It  is 
not  a  glucoside  and  its  constitution  is  unknown ;  it  forms  white  crystals  which 
have  a  slightly  acrid,  bitter  taste,  are  almost  insoluble  in  water,  have  a  neutral 
reaction,  and  impart  to  cold  concentrated  sulphuric  acid  at  first  a  yellow  color, 
which  gradually  changes  to  scarlet. 

Picrotoxin  C30H34013.  Obtained  from  the  seed  of  Anamirta  paniculata.  Like 
elaterin,  this  is  not  a  glucoside  and  its  constitution  is  unknown.  The  white 
crystals  have  a  very  bitter  taste,  are  somewhat  soluble  in  water,  have  a  neutral 
reaction,  and  impart  to  cold  concentrated  sulphuric  acid  a  golden-yellow  color, 
very  gradually  changing  to  reddish-brown,  and  showing  a  brown  fluorescence. 


47.  AMINES  AND  AMIDES.    CYANOGEN  COMPOUNDS. 

Forms  of  nitrogen  in  organic  compounds.  Nitrogen  may  be 
present  iu  organic  compounds  in  three  forms,  viz.,  ammonia,  cyanogen, 
nitric  acid,  or  derivatives  of  these  compounds.  Substances  containing 
nitrogen  in  the  nitric  acid  form  may  be  obtained  by  combination  of 
nitric  acid  with  organic  basic  substances,  when  salts  are  formed,  or 
with  alcohols,  when  compound  ethers  result.  In  some  cases  the 
nitric  acid  radical  NO2  may  replace  one  or  more  hydrogen  atoms  in 

QUESTIONS. — 451.  To  which  group  of  substances  is  the  term  "carbohy- 
drates" applied?  452.  State  the  general  properties  of  carbohydrates.  453. 
Mention  the  three  groups  of  carbohydrates,  and  the  composition  and  charac- 
teristics of  the  members  of  each  group.  454.  Mention  some  fruits  in  which 
grape-sugar,  and  some  plants  in  which  cane-sugar  is  found.  455.  What  is  the 
difference  between  grape-sugar  and  cane-sugar,  and  by  what  tests  can  they  be 
distinguished  ?  456.  From  what  source,  and  by  what  process,  is  milk-sugar 
obtained  ?  457.  What  is  starch,  what  are  its  properties,  by  what  tests  can  it 
be  recognized,  and  what  substance  is  formed  when  diastase  or  dilute  acids  act 
upon  it  ?  458.  Where  is  cellulose  found  in  nature,  and  what  are  its  proper- 
ties? 459.  What  three  compounds  may  be  obtained  by  the  action  of  nitric 
acid  upon  cellulose,  and  what  are  they  used  for?  460.  What  substances  are 
termed  glucosides  ?  Mention  some  of  the  more  important  glucosides. 


356  CONSIDERATION  OF  CARBON  COMPOUNDS. 

carbon  compounds.  Organic  substances  containing  nitrogen  in  the 
nitric  acid  form  do  not  occur  in  nature,  but  are  obtained  exclusively 
by  artificial  means,  generally  by  treatment  of  the  organic  substance 
with  concentrated  nitric  acid ;  many  of  these  compounds  are  more  or 
less  explosive,  as,  for  instance,  cellulose  trinitrate,  glyceryl  nitrate, 
and  others. 

Cyanogen  compounds  contain  nitrogen  in  the  form  of  cyanogen, 
CN,  a  radical  the  compounds  of  which  will  be  considered  hereafter. 

Organic  compounds  containing  nitrogen  in  the  ammonia  form  are 
chiefly  those  known  as  amines  or  amides,  organic  bases  or  alkaloids. 
(Albuminous  substances  also  contain  nitrogen  in  the  ammonia  form). 

Amines.  Whenever  the  hydrogen  of  ammonia  is  replaced  by 
alcoholic  radicals  (or  hydrocarbon  residues)  compounds  are  formed 
which  are  termed  amines.  For  instance  : 


H/~^    TT  f^    TT  f^\    T_T  ^    TT 

/  /^2*-*5  .X^^-^S  /^2-*-*-5  /^        3 

Or 

NH3,          N(C2H5)H2,       N(C2H5)2H,      N(C2H5)3,  NCH3.C2H5.C4H9. 

Ammonia.         Ethylamine.        Diethylamine.    Triethylamine.    Methyl-ethyl-butylamine. 

Amines  resemble  ammonia  in  their  chemical  properties  ;  they  are, 
like  ammonia,  basic  substances;  they  combine  with  acids  directly 
and  without  elimination  of  water,  thus  : 


NH3    +    HC1    = 

N(C2H5)3    -j-    HC1    =    N(C2H5)3HC1. 
Triethylamine.  Triethylamine 

chloride. 

Amides  are  substances  derived  from  ammonia  by  replacement  of 
hydrogen  atoms  by  acid  radicals.     Thus  : 

2H30  /C2H30 


H  H  H 

Ammonia.  Acetamide.  Diacetamide.       Carbamide  or  urea. 

Amides  also  resemble  ammonia  in  their  chemical  properties  ;  to  a 
less  extent,  however,  than  amines,  because  the  acid  radicals  have  a 
tendency  to  neutralize  the  basic  properties  of  ammonia  : 

Formamide,  N(CHO)H2,  is  a  colorless  liquid,  obtained  by  heating  ethyl 
formate  with  an  alcoholic  solution  of  ammonia.  This  compound  is  of  interest 
because  it  combines  with  chloral,  forming  Chloral/  ormamide  (  Chloralamide)  } 
N(CHO)H2.C2HC130,  a  substance  recently  used  as  a  hypnotic.  It  is  a  color- 
less, odorless,  crystalline  substance,  having  a  faintly  bitter  taste.  It  is  soluble 
in  20  parts  of  cold  water  and  in  1.5  parts  of  alcohol.  By  heating  the  aqueous 
solution  to  60°  C.  (140°  F.)  it  is  decomposed  into  chloral  and  formamide. 


AMINES  AND  AMIDES.     CYANOGEN  COMPO  UNDS.  357 

Amido-acids  are  acids  in  which  hydrogen  has  been  replaced  by 
NH2.     Thus,  amido-acetic  acid,  also  known  as  glycocoll  or  glycine,  is 

represented  by  the  formula  C2H3(NH2)O2  or  CH2/        2    ;  it  is  a  sub- 


stance which  has  both  acid  and  basic  properties,  and  is  a  product  of 
the  decomposition  of  either  glycocholic  or  hippuric  acid  by  hydro- 
chloric acid. 

Amido-formic  acid  or  carbamic  acid,  CH.NH2.O2,  is  the  acid  which, 
in  the  form  of  the  ammonium  salt,  is  a  constituent  of  the  commercial 
ammonium  carbonate.  It  is  formed  by  the  direct  action  of  carbon 
dioxide  upon  ammonia  : 

C02    +    2NH3    =    C.NH4.NH202. 

Formation  of  amines  and  amides.  These  substances  are  found 
as  products  of  animal  life  (urea),  of  vegetable  life  (alkaloids),  of 
destructive  distillation  (aniline,  pyridine),  of  putrefaction  (ptomaines), 
and  may  also  be  produced  synthetically  —  for  instance,  by  the  action 
of  ammonia  upon  the  chloride  or  iodide  of  an  alcohol  or  acid  radical  : 
C2H5.I  +  NH3  :  HI  +  NH2C2H5. 

Ethyl  iodide.      Ammonia.    Hydriodic       Ethylamine. 
acid. 

C2H3O.C1     +    2NH3    =       NH4C1     -f     NH2.C2HSO. 

Acetyl  Ammonia.       Ammonium  Acetamide. 

chloride.  chloride. 

Amines  may  also  be  formed  by  the  action  of  nascent  hydrogen 
upon  the  cyanides  of  the  alcoholic  radicals  : 

CH3CN    +    4H    =    NH2C2H6. 
Methyl  cyanide.  Ethylamine. 

Amines  may  in  some  cases  be  formed  by  the  action  of  nascent 
hydrogen  upon  mtro-compounds  ;  the  manufacture  of  aniline  depends 
on  this  decomposition  : 

C6H5N02    +     6H    =    2H20     +     NH2.C6H5. 

Nitro-benzene.    Hydrogen.        Water.  Phenylamine, 

or  aniline. 

Occurrence  of  organic  bases  in  nature.  The  various  organic 
basic  substances  found  in  nature  are  either  amines  (compounds  con- 
taining carbon,  hydrogen,  and  nitrogen  only),  or  amides  (compounds 
containing,  besides  the  three  elements  named,  also  oxygen).  But  a 
small  number  of  organic  bases  is  found  in  the  animal  system,  urea 
being  the  most  important  one.  In  plants  organic  bases  are  more 
frequently  met  with,  and  are  grouped  together  under  the  name  of 
alkaloids.  While  the  constitution  of  many  alkaloids  has  not  yet 
been  sufficiently  explained,  we  know  that  many  of  them  are  deriv- 


358  CONSIDERATION  OF  CARBON  COMPOUNDS. 

atives  of  aromatic  compounds,  for  which  reason  the  consideration  of 
the  whole  group  will  be  deferred  until  benzene  and  its  derivatives 
are  spoken  of.  The  large  number  of  basic  substances  found  in  putre- 
fying matter  and  termed  ptomaines  will  also  be  considered  later  on. 

Cyanogen  compounds.  Cyanogen  itself  does  not  occur  in  nature, 
but  compounds  of  it  are  found  in  a  few  plants  (amygdalin),  and  also 
in  some  animal  fluids  (saliva  contains  sodium  sulphocyanate).  Gases 
issuing  from  volcanoes  (or  from  iron  furnaces)  sometimes  contain 
cyanogen  compounds. 

The  univalent  residue  cyanogen,  — C=N,  or  CN,  was  the  first 
compound  radical  distinctly  proved  to  exist,  and  isolated  by  Gay- 
Lussac  in  1814.  The  name  cyanogen  signifies  "  generating  blue/'  in 
allusion  to  the  various  blue  colors  (Prussian  and  TurnbulPs  blue) 
containing  it.  (The  symbol  Cy,  sometimes  used  in  place  of  CN,  has 
been  adopted  merely  to  simplify  the  writing  of  formulas  of  cyanogen 
compounds). 

Cyanogen  and  its  compounds  show  much  resemblance  to  the  halo- 
gens and  their  compounds,  as  indicated  by  the  composition  of  the 
following  substances : 

C1C1,  HC1,  KI,  HC1O, 

Chlorine,  Hydrochloric  Potassium  Hypochlorous 

acid.  iodide.  acid. 

CNCN,  HBr,  KCN,  HCNO, 

Cyanogen.  Hydrobromic  Potassium  Cyanic  acid. 

acid.  cyanide. 

CNC1,  HCN,  AgCN,  HCNS, 

Cyanogen  Hydrocyanic  Silver  Sulphocyanic 

chloride.  acid.  cyanide.  acid. 

Dicyanogen,  (CN)2.  The  unsaturated  radical  CN  does  not  exist 
as  such  in  a  free  state,  but  combines  whenever  liberated  with  another 
CN,  forming  dicyanogen.  It  may  be  obtained  by  heating  mercuric 

cyanide : 

Hg(CN)2    =    Hg    +     2CN. 

It  is  a  colorless  gas,  having  an  odor  of  bitter  almonds,  and  burn- 
ing with  a  purple  flame,  forming  carbon  dioxide  and  nitrogen ;  it  is 
soluble  in  water,  and  may  be  converted  into  a  colorless  liquid  by 
pressure ;  it  acts  as  a  poison,  both  to  animal  and  vegetable  life,  even 
when  present  in  but  small  proportions  in  the  air. 

Hydrocyanic  acid,  HCN  =  27  (Cyanhydric  acid,  Hydrogen 
cyanide,  Prussic  acid).  This  compound  is  found  in  the  water  distilled 
from  the  disintegrated  seeds  or  leaves  of  amygdalus,  primus,  laurus, 


AMINES  AND  AMIDES.     CYANOGEN  COMPOUNDS.  359 

etc.  It  is  also  found  among  the  products  of  the  destructive  distilla- 
tion of  coal,  and  is  formed  by  a  great  number  of  chemical  decompo- 
sitions. For  instance: 

By  passing  ammonia  over  red-hot  charcoal : 

4NH3    -f    30    =    2(NH4CN)     +     CH4. 
Ammonia.       Carbon.        Ammonium  Methane, 

cyanide. 

By  the  action  of  ammonia  on  chloroform  : 

CHC13    +     NH3    =    HCN     +     3HC1. 
Chloroform.  Hydrocyanic     Hydrochloric 

acid.  acid. 

By  heating  ammonium  formate  to  200°  C.  (392°  F.)  : 

NH4CH02    :       HCN    +    2H2O. 

Ammonium       Hydrocyanic         Water, 
formate.  acid. 

By  the  action  of  hydrosulphuric  acid  upon  mercuric  cyanide : 

Hg(CN2)     +     H2S    ==    HgS    -f     2HCN. 
By  the  decomposition  of  alkali  cyanides  by  diluted  acids : 

KCN    -f-    HC1    =    KC1    -f     HCN. 
By  the  action  of  hydrochloric  acid  upon  silver  cyanide  : 

AgCN    -f    HC1    =    AgCl     +    HCN. 
By  distilling  potassium  ferrocyanide  with  diluted  sulphuric  acid : 

2K,Fe(CN)6    +     6(H2S04)     =        K2Fe2(CN)6    +    6KHSO,    +     6HCN. 

Potassium  Sulphuric  Potassium  ferrous     Potassium  acid     Hydrocyanic 

ferrocyanide.  acid.  ferrocyanide.  sulphate.  acid. 

Experiment  55.  Place  20  grammes  of  potassium  ferrocyanide  and  40  c.c.  of 
water  into  a  boiling-flask  of  about  200  c.c.  capacity ;  provide  the  flask  with  a 
funnel-tube  and  connect  it  with  a  suitable  condenser,  the  exit  of  which  should 
dip  into  60  c.c.  of  diluted  alcohol,  contained  in  a  receiver,  which  latter  should 
be  kept  cold  by  ice  during  the  operation.  After  having  ascertained  that  all 
the  joints  are  tight,  add  through  the  funnel-tube  a  previously  prepared  mixture 
of  15  grammes  of  sulphuric  acid  and  20  c.c.  of  water.  Apply  heat  and  slowly 
distil  until  there  is  little  liquid  left  with  the  salts  remaining  in  the  flask. 

Determine  the  strength  of  the  alcoholic  solution  of  hydrocyanic  acid  thus 
prepared  volumetrically  and  dilute  it  with  water  until  it  contains  exactly  two 
per  cent,  of  HCN. 

Pure  hydrocyanic  acid  is,  at  a  temperature  below  26°  C.  (78.8°  F.), 
a  colorless,  mobile  liquid,  of  a  penetrating,  characteristic  odor  resem- 
bling that  of  bitter  almonds  ;  it  boils  at  26.5°  C.  (80°  F.)  and  crystal- 
lizes at  — 15°  C.  (5°  F.).  It  is  readily  soluble  in  water,  and  a  2  per 
cent,  solution  is  the  diluted  hydrocyanic  acid,  Acidum  hydrocyanicum 
dilutum. 


360  CONSIDERATION  OF  CARBON  COMPOUNDS. 

According  to  the  U.  S.  P.,  this  diluted  acid  is  made  either  by  the 
decomposition  of  potassium  ferrocyanide  by  diluted  sulphuric  acid  in 
a  retort,  the  delivery-tube  of  which  passes  into  a  receiver  containing 
water,  by  which  the  liberated  gas  is  absorbed,  this  liquid  being  after- 
ward diluted  with  a  sufficient  quantity  of  water  to  make  a  2  per  cent, 
solution,  or  it  is  made  extemporaneously  by  the  decomposition  of  6 
parts  by  weight  of  silver  cyanide  by  5  parts  of  hydrochloric  acid, 
diluted  with  55  parts  of  water,  allowing  the  silver  chloride  to  sub- 
side and  pouring  off  the  clear  liquid. 

The  diluted  acid  has  the  characteristic  odor  of  bitter  almonds,  a 
slightly  acid  reaction,  and  is  completely  volatilized  by  heating. 
Whilst  the  pure  acid  is  very  readily  decomposed  by  exposure  to  light, 
etc.,  the  dilute  acid  is  fairly  stable. 

Potassium  cyanide,  Potassii  cyanidum,  KCN  =  65.  The  pure 
salt  may  be  obtained  by  passing  hydrocyanic  acid  into  an  alcoholic 
solution  of  potassium  hydroxide.  The  commercial  article,  however, 
is  a  mixture  of  potassium  cyanide  with  potassium  cyanate.  It  is 
obtained  by  fusing  potassium  ferrocyanide  with  potassium  carbonate 
in  a  crucible,  when  potassium  cyanide  and  cyanate  are  formed,  whilst 
carbon  dioxide  escapes,  and  metallic  iron  is  set  free  and  collects  on 
the  bottom  of  the  crucible.  The  decomposition  is  as  follows  : 

K4Fe(CN)6    -f     K2CO3    =  =    5KCN     +     KCNO     +     Fe    +     CO2. 
Potassiiim  Potassium         Potassium          Potassium  Iron.  Carbon 

ferrocyanide.  carbonate.         cyanide.  cyanate.  dioxide. 

Potassium  cyanide,  U.  S.  P.,  should  contain  at  least  90  per  cent, 
of  the  pure  salt ;  it  is  a  white,  deliquescent  substance,  odorless  when 
perfectly  dry,  but  emitting  the  odor  of  hydrocyanic  acid  when  moist ; 
it  is  soluble  in  about  2  parts  of  water ;  this  solution  has  an  alkaline 
reaction  and  decomposes  slowly  in  the  cold,  but  rapidly  on  heating, 
with  the  formation  of  potassium  and  ammonium  carbonates : 

2KCNO    +    4H2O    =    K2CO3    -f    (NH4)2CO3. 

Potassium  cyanides  and  other  alkali  cyanides  show  a  tendency  to 
combine  with  the  cyanides  of  heavy  metals,  forming  a  number  of 
double  cyanides,  such  as  the  cyanide  of  sodium  and  silver,  NaCN. 
AgCN,  etc. 

Silver  cyanide,  Argenti  cyanidum,  AgCN  =  133.7  (Cyanide  of 
silver).  A  white  powder,  obtained  by  precipitating  solution  of 
potassium  cyanide  with  silver  nitrate.  It  is  insoluble  in  water, 
slowly  soluble  in  water  of  ammonia ;  evolves  cyanogen  when  heated, 
metallic  silver  being  left. 


AMINES  AND  AMIDES.     CYANOGEN  COMPOUNDS.  361 

Mercuric  cyanide,  Hydrargyri  cyanidum,  Hg-(CN)2.  A  white 
crystalline  salt,  obtained  by  dissolving  mercuric  oxide  in  hydrocyanic 
acid  ;  it  is  soluble  in  water  and  alcohol  and  evolves  cyanogen  when 
heated. 

Analytical  reactions  for  hydrocyanic  acid. 
(Potassium  cyanide,  KCN,  may  be  used.) 

1.  Hydrocyanic  acid,  or  soluble  cyanides,  give  with  silver  nitrate 
a  white  precipitate  of  silver  cyanide,  which  is  sparingly  soluble  in 
ammonia,  soluble  in  alkali  cyanides  or  thiosulphates,  but  insoluble 
in  diluted  nitric  acid.     Concentrated  nitric  acid  dissolves  it  with 
decomposition : 

HCN     +     AgN03    =    AgCN    +    HNO3. 

2.  Hydrocyanic  acid  mixed  with  ammonium  hydric  sulphide  and 
evaporated  to  dryness  forms  sulphocyanic  acid,  which,  upon  being 
slightly  acidulated  with  hydrochloric  acid,  gives  with  ferric  chloride 
a  blood-red  color  of  ferric  sulphocyanate.     (Excess  of  ammonium 
sulphide  must  be  avoided.) 

3.  Hydrocyanic  acid,  or  soluble  cyanides,  give,  when  mixed  with 
ferrous  and  ferric  salts  and  potassium  hydroxide,  a  greenish  precipi- 
tate, which,  upon  being  dissolved  in  hydrochloric  acid,  forms  a  pre- 
cipitate of  Prussian  blue,  Fe4(FeC6N6)3.     This  reaction  depends  on 
the  formation  of  potassium  ferrocyanide  by  the  action  of  the  cyanogen 
upon  both  the  potassium  of  the  potassium  hydroxide  and  the  iron  of 
the  ferrous  salt.     In  alkaline  solutions,  the  blue  precipitate  does  not 
form,  for  which  reason  hydrochloric  acid  is  added. 

4.  Hydrocyanic  acid  heated  with  dilute  solution  of  picric  acid  gives 
a  deep-red  color  on  cooling. 

In  cases  of  poisoning,  the  matter  under  examination  is  distilled  (if  neces- 
sary after  the  addition  of  water)  from  a  retort  connected  with  a  cooler.  To 
the  distilled  liquid  the  above  tests  are  applied.  If  the  substance  under  ex- 
amination should  have  an  alkaline  or  neutral  reaction,  the  addition  of  some 
sulphuric  acid  may  be  necessary  in  order  to  liberate  the  hydrocyanic  acid. 
The  objectionable  feature  to  this  acidifying  is  the  fact  that  non-poisonoua 
potassium  ferrocyanide  might  be  present,  which  upon  the  addition  of  sulphuric 
acid  would  liberate  hydrocyanic  acid.  In  cases  where  the  addition  of  an  acid 
becomes  necessary,  a  preliminary  examination  should,  therefore,  decide 
whether  or  not  ferro-  or  ferricyanides  are  present. 

Antidotes.  Hydrocyanic  acid  is  a  powerful  poison  both  when  inhaled  or 
swallowed  in  the  form  of  the  acid  or  of  soluble  cyanides.  As  an  antidote  is 
recommended  a  mixture  of  ferrous  sulphate  and  ferric  chloride  with  either 
sodium  carbonate  or  magnesia.  The  action  of  this  mixture  is  explained  in 


362  CONSIDERATION  OF  CARBON  COMPOUNDS. 

the  above  reaction  3,  the  object  being  to  convert  the  soluble  cyanide  into  an 
insoluble  ferrocyanide  of  iron.  In  most  cases  of  poisoning  by  hydrocyanic 
acid  there  is,  however,  no  time  for  the  action  of  such  an  antidote,  in  conse- 
quence of  the  rapidity  of  the  action  of  the  poison,  and  the  treatment  is  chiefly 
directed  to  the  maintenance  of  respiration  by  artificial  means. 

Cyanic  acid,  HCNO,  and  Sulphocyanic  acid,  HCNS,  are  both 
colorless  acid  liquids,  the  salts  of  which  are  known  as  cyanates  and 
sulpho-cyanates.  These  salts  are  obtained  from  alkali  cyanides  by 
treating  them  with  oxidizing  agents  or  by  boiling  their  solutions  with 
sulphur,  when  either  oxygen  or  sulphur  is  taken  up  by  the  alkali 
cyanide : 

KCN     +     O     =    KCNO     =     Potassium  cyanate. 
KCN     +     S     =    KCNS    :        Potassium  sulphocyanate. 

The  acids  themselves  may  be  liberated  from  their  salts  by  dilute 
mineral  acids.  Sulphocyanates  give  with  ferric  salts  a  deep-red 
color,  which  is  not  affected  by  hydrochloric  acid,  but  disappears  on 
the  addition  of  mercuric  chloride. 


Me tallo cyanides.  Cyanogen  not  only  combines  with  metals  to 
form  the  true  cyanides,  which  may  be  looked  upon  as  derivatives  of 
hydrocyanic  acid,  but  cyanogen  also  enters  into  combination  with 
certain  metals  (chiefly  iron),  forming  a  number  of  complex  radicals, 
which  upon  combining  with  hydrogen  form  acids,  or  with  basic 
elements  form  salts.  It  is  a  characteristic  feature  of  the  compound 
cyanogen  radicals,  thus  formed,  that  the  analytical  characters  of  the 
metals  (iron,  etc.)  entering  into  the  radical  are  completely  hidden. 
Thus,  the  iron  in  ferro-  or  ferricyanides  is  not  precipitated  by  either 
alkalies,  soluble  carbonates,  ammonium  sulphide,  or  any  of  the  com- 
mon reagents  for  iron,  and  its  presence  can  only  be  demonstrated  by 
these  reagents  after  the  organic  nature  of  the  compound  has  been 
destroyed  by  burning  it  (or  otherwise),  when  ferric  oxide  is  left, 
which  may  be  dissolved  in  hydrochloric  acid  and  tested  for  in  the 
usual  manner. 

The  principal  iron-cynogen  radicals  are  ferrocyanogen  [Feu 
(CNy]^,  smdferricyanogen  [Fe/^CN")^1]™.  These  two  radicals  con- 
tain iron  in  the  ferrous  and  ferric  state  respectively,  and  form,  upon 
combining  with  hydrogen,  acids  which  are  known  as  hydroferrocyanic 
add,  H4Fe(CN)6  (tetrabasic),  and  hydroferricyanic  acid,  H6Fe2(C!N")12 
(hexabasic) ;  the  salts  of  these  acids  are  termed  ferrocyanides  and 
ferricvanides. 


AMINES  AND  AMIDES.     CYANOGEN  COMPOUNDS.          363 

Potasssium  ferrocyanide,  Potassii  ferrocyanidum,  K4Pe(CN)6. 
3H2O  =  421.9  (Yellow  prussiate  of  potash).  This  salt  is  manu- 
factured on  a  large  scale  by  heating  refuse  animal  matter  (waste 
leather,  horns,  hoofs,  etc.)  with  potassium  carbonate  and  iron  (filings, 
etc.).  The  fused  mass  is  boiled  with  water,  and  from  the  solution 
thus  formed  the  crystals  separate  on  cooling. 

The  nitrogen  and  carbon  of  the  organic  matter  (heated  as  above 
stated)  combine,  forming  cyanogen,  which  enters  into  combination 
first  with  potassium  and  afterward  with  iron. 

Potassium  ferrocyanide  forms  large,  translucent,  pale  lemon-yellow, 
soft,  odorless,  non-poisonous,  neutral  crystals,  easily  dissolving  in 
water,  but  insoluble  in  alcohol. 

Analytical  reactions : 

1.  Ferrocyanides  heated  on  platinum  foil  burn  and  leave  a  residue 
of  (or  containing)  ferric  oxide. 

2.  Ferrocyanides  heated  with  concentrated  sulphuric  acid  evolve 
carbonic  oxide  ;  with  dilute  sulphuric  acid  liberate  hydrocyanic  acid ; 
with  concentrated  hydrochloric  acid  liberate  hydroferrocyanic  acid. 

3.  Soluble  ferrocyanides  give  a  blue  precipitate  with  ferric  salts 
(Plate  L,  5) : 

3K4Fe(CN)6    +     2Fe2Cl6    =    12KC1     -f     Fe4(FeC6N6)3. 

Potassium  Ferric  Potassium  Ferric  ferro 

ferrocyanide.  chloride.  chloride.  cyanide. 

The  blue  precipitate  of  ferric  ferrocyanide,  or  Prussian  blue,  is 
insoluble  in  water  and  diluted  acids,  soluble  in  oxalic  acid  (blue 
ink),  and  is  decomposed  by  alkalies  with  separation  of  brown  ferric 
hydroxide  and  formation  of  potassium  ferrocyanide.  The  addition 
of  an  acid  restores  the  blue  precipitate. 

4.  Soluble  ferrocyanides  give  with  cupric  solutions  a  brownish-red 
precipitate  of  cupric  ferrocyanide.     (Plate  III.,  5.) 

5.  Soluble  ferrocyanides  produce,  with  solutions  of  silver,  lead,  and 
zinc,  white  precipitates  of  the  respective  ferrocyanides. 

6.  Ferrocyanides  give  with   ferrous  salts  a  white  precipitate  of 
ferrous  ferrocyanide,  soon  turning  blue  by  absorption  6f  oxygen. 
(Plate  I.,  4.) 

Potassium  ferricyanide,  KcPe2(CN)12  (Red  prussiate  of  potash). 
Obtained  by  passing  chlorine  through  solution  of  potassium  ferro- 
cyanide : 

2K4Fe(CN)6     +     2C1        =    2KC1     +     K6Fe2(CN)12. 

Potassium  Chlorine.      Potassium  Potassium 

ferrocyanide.  chloride.  ferricyanide. 


364  CONSIDERATION  OF  CARBON  COMPOUNDS. 

While  apparently  this  decomposition  consists  merely  in  a  removal 
of  two  atoms  of  potassium  from  two  molecules  of  potassium  ferro- 
cyanide,  the  change  is  actually  more  complete,  as  the  atoms  arrange 
themselves  differently,  the  iron  passing  also  from  the  ferrous  to  the 
ferric  state. 

Potassium  ferricyanide  crystallizes  in  red  prisms,  soluble  in  water. 
It  forms,  with  ferrous  solutions,  a  blue  precipitate  of  ferrous  ferricy- 
anide, or  TurnbuWs  blue : 

K6Fe2(CN)12    +    3FeS04    =  =  3K2SO4    +     Fe3Fe2(CN)12. 

With  ferric  solutions  no  precipitate  is  produced  by  potassium  ferri- 
cyanide, but  the  color  is  changed  to  a  deep  brown. 

Nitro-cyan-methane,  CH2.CN.N02  (Fulminic  acid}.  This  substance  may  be 
looked  upon  as  a  derivative  of  methane,  CH4,  in  which  two  atoms  of  hydro- 
gen are  replaced  by  cyanogen  and  NO2  respectively.  It  is  not  known  in  the 
separate  state,  but  its  combinations  with  metals  are  well  known,  especially 
mercuric  fulminate,  which  is  manufactured  and  used  as  an  explosive  in  percus- 
sion caps,  etc.  It  is  made  by  adding  alcohol  to  a  solution  of  mercury  in  nitric 
acid.  Silver  fulminate  can  be  obtained  by  a  similar  process. 

48.  BENZENE   SERIES.     AROMATIC  COMPOUNDS. 

General  remarks.  It  has  been  stated  before  that  all  organic  com- 
pounds may  be  looked  upon  as  derivatives  of  either  methane,  CH4, 
or  benzene,  C6H6,  these  derivatives  being  often  spoken  of  as  fatty  and 
aromatic  compounds  respectively.  The  term  aromatic  compounds 
was  given  to  these  substances  on  account  of  the  peculiar  and  fragrant 
odor  possessed  by  many,  though  not  by  all  of  them.  Benzene  and 

QUESTIONS.  461.  What  are  the  three  chief  forms  in  which  nitrogen  enters 
into  organic  compounds  ?  462.  What  are  amines  and  amides ;  in  what  re- 
spects do  they  resemble  ammonia  compounds  ?  463.  What  is  cyanogen,  what 
is  dicyanogen,  and  how  is  the  latter  obtained?  464.  How  does  cyanogen 
occur  in  nature,  and  which  non-metallic  elements  does  it  resemble  in  the  con- 
stitution of  various  compounds?  465.  Mention  some  reactions  by  which 
hydrocyanic  acid  is  formed,  and  state  the  two  processes  by  which  the  official 
diluted  acid  is  obtained.  What  strength  and  what  properties  has  this  acid  ? 
466.  State  the  composition  of  pure  potassium  cyanide  and  of  the  commercial 
article.  How  is  the  latter  made?  467.  Give  reactions  for  hydrocyanic  acid 
and  cyanides.  468.  Explain  the  constitution  and  give  the  composition  of 
ferro-  and  ferricyanides.  469.  Give  composition,  mode  of  manufacture,  and 
tests  of  potassium  ferrocyanide.  470.  What  is  red  prussiate  of  potash,  how 
is  it  obtained,  and  by  what  reactions  can  it  be  distinguished  from  the  yellow 
prussiate  ? 


BENZENE  SERIES.    AROMATIC  COMPOUNDS.  365 

methane  derivatives  differ  considerably  in  many  respects,  and,  as  a 
general  rule,  aromatic  compounds  cannot  be  converted  into  fatty 
compounds,  or  the  latter  into  aromatic  compounds,  without  suffering 
the  most  vital  decomposition  of  the  molecule,  and  in  many  cases  this 
transformation  cannot  be  accomplished  at  all. 

On  the  average,  aromatic  compounds  are  richer  in  carbon  than  fatty 
compounds,  containing  of  this  element  at  least  6  atoms  ;  when  decom- 
posed by  various  methods,  aromatic  compounds,  in  many  cases,  yield 
benzene  as  one  of  the  products  ;  most  aromatic  substances  have  anti- 
septic properties,  and  none  of  them  serves  as  animal  food,  although 
quite  a  number  are  taken  into  the  system  in  small  quantities,  as,  for 
instance,  some  essential  oils,  caffeine,  etc. 

While  some  aromatic  compounds  are  products  of  vegetable  life, 
many  of  them  (like  benzene  itself)  are  obtained  by  destructive  distil- 
lation, and  are,  therefore,  contained  in  coal-tar,  from  which  quite  a 
number  are  separated  by  fractional  distillation. 

The  constitution  of  benzene  is  best  explained  by  assuming  that  of 
the  4  X  6  =  24  affinities  of  the  6  carbon  atoms,  18  affinities  are  lost 
by  uniting  the  carbon  atoms  into  a  closed  chain,  while  but  6  affinities 
are  left  unprovided  for  and  may  be  saturated  by  other  elements  or 
groups  of  elements. 

The  carbon  chain  of  aromatic  compounds  and  benzene  may  be 
graphically  represented  thus  : 

1  H 

6\CAC/2  H\CAC/H 


d, 

6          0^   \3  H/    \C^    \H 

i  A 

It  has  been  found  that  whenever  one  atom  or  one  radical  replaces 
hydrogen  in  benzene,  the  product  obtained  is  the  same,  no  matter  by 
what  method  the  change  is  brought  about.  Thus  we  know  but  one 
mono-brom-benzene,  C6H5Br,  one  nitro-benzene,  C6H5NO2,  etc. 

It  is  different  when  two  or  more  atoms  or  radicals  (of  the  same 
kind)  replace  hydrogen  in  benzene,  since  it  has  been  found  that  in 
this  case  often  isomeric  compounds  are  formed. 

For  instance,  we  know  three  different  substances  which  have  been 
obtained  by  replacement  of  two  hydrogen  atoms  in  benzene  by  two 
hydroxyl  groups.  This  would  indicate  that  it  makes  a  difference,  as 
far  as  the  properties  of  a  compound  are  concerned,  in  which  relative 


366  CONSIDERATION  OF  CARBON  COMPOUNDS. 

position  the  introduced  radicals  stand  to  one  another,  and  while  we 
have  no  proof  whatever  in  regard  to  this  position,  yet  we  often  repre- 
sent it  graphically,  as,  for  instance,  in  the  following  three  cases,  where 
the  two  groups  OH  replace  hydrogen  in  different  positions  : 

OH  OH 

C. 


OH 

| 

H           CL         OH 

\cx  ^cx 

H, 

A      i 

xUv      xMv 

Hx    XCX    XH 

jj 

i 

"pi5 

\  x 


A 


Ortho-position.  Meta-position.  Para-position. 

1.2.  1.3.  L4. 

Designating  the  hydrogen  atoms  in  benzene  with  numbers,  thus  : 

123456 

C6  H  H  H  H  H  H,  the  above  3  compounds  show  that  in  one  case 
the  hydrogen  atoms  1  and  2,  in  the  second  1  and  3,  in  the  third  1 
and  4  have  been  replaced  by  OH.  The  compounds  formed  in  this 
way  are  distinguished  as  ortho-,  rneta-,  and  para-compounds. 

The  molecular  formula  of  the  above  three  compounds  is  C6H6O2, 
apparently  indicating  benzene  in  combination  with  two  atoms  of 
oxygen  or  dioxybenzene  ;  actually  they  are  dihydroxy  benzene. 

1         2 

Ortho-dihydroxy  benzene,  C6H4OHOH,  is  known  as  pyro-catechin, 

1        3 

raeta-dihydroxy   benzene,    C6H4OHOH,  as   resorcin,  and  para-di- 

1         4 

hydroxy  benzene,  C6H4OHOH,  as  hydroquinone. 

Benzene  series  of  hydrocarbons.  By  replacing  the  hydrogen 
atoms  in  benzene  by  methyl,  CH3,  a  series  of  hydrocarbons  is  formed 
having  the  general  composition  CnH2n—  e-  To  this  benzene  series 
belong  : 

B.  P. 

Benzene      .        .        .  C6  H6  ...............  80°  C. 

Toluene      .        .        .  C7  H8  =  C6H5CH3  110 

Xylene        .        .        .  C8  H10  =  C6H4(CH3)2  142 

•Cumene      .        .        .  C9  H12  =  C6H3(CH3)3  151 

Cymene       .        .        .  C10HU  =  (C6H2(CH3)4?  175 

Penta-methyl-benzene  C^H^  =  C6H(CH3)5  188 

Hexa-methyl-benzene  C12H18  :   :  C6(CH3)6  202 

The  first  four  members  of  this  series  are  found  in  coal-tar  ;  the 
fifth  member,  cymene,  C10H14,  occurs  in  the  oil  of  thyme  ;  the  last 
two  have  been  obtained  by  synthetical  processes.  While  but  one 
toluene  is  known,  the  higher  members  form  quite  a  number  of  iso- 
meric  compounds.  Cymene,  found  in  the  oil  of  thyme,  is,  for 


BENZENE  SERIES.    AROMATIC  COMPOUNDS.  367 

instance,  not  the  tetra-methyl-benzene,  but  the  para-methyl-propyl- 
benzene,  C6H4  CH3.C3H7.  This  compound  is  of  interest  on  account 
of  its  close  relation  to  the  terpenes  and  camphors,  which  will  be 
spoken  of  later. 

Benzene,  C6H6  (Benzol).  When  coal-tar  is  distilled,  products  are 
obtained  which  are  either  lighter  or  heavier  than  water,  and  by  col- 
lecting the  distillate  in  water  a  separation  into  so  called  light  oil 
(floating  on  the  water)  and  heavy  oil  (sinking  beneath  the  water)  is 
accomplished.  Benzene  is  found  in  the  light  oil  and  obtained  from 
it  by  distillation  after  phenol  has  been  removed  by  treatment  with 
caustic  soda  and  some  basic  substances  by  means  of  sulphuric  acid. 
Pure  benzene  may  be  obtained  by  heating  benzoic  acid  with  calcium 
hydroxide : 

C6H5.CO2H     +     Ca(OH)2    =   =     CaCO3     +     H2O     +     C6H8. 

Experiment  56.  Mix  25  grammes  of  benzoic  acid  with  40  grammes  of  slaked 
lime  and  distil  from  a  dry  flask,  connected  with  a  condenser.  Add  to  the  dis- 
tilled fluid  a  little  calcium  chloride  and  redistil  from  a  small  flask.  The 
product  obtained  is  pure  benzene.  Notice  that  it  solidifies  when  placed  in  a 
freezing  mixture  of  ice  and  common  salt.  Observe  the  analogy  between  Ex- 
periments 56  and  40.  In  one  case  a  fatty  acid  is  decomposed  by  an  alkali  with 
liberation  of  methane,  in  the  other  an  aromatic  acid  with  liberation  of  benzene, 
the  carbonate  of  the  decomposing  hydroxide  being  formed  in  both  cases. 

Pure  benzene  is  a  colorless,  highly  volatile  liquid,  having  a  peculiar, 
aromatic  odor  and  a  specific  gravity  of  0.884;  it  boils  at  80.5°  C. 
(177°  F.)  and  solidifies  at  0°  C.  (32°  F.)  ;  it  is  an  excellent  solvent 
for  fats,  oils,  resins,  and  many  other  organic  substances. 

Nitro-benzene,  C6H5.NO2.  When  benzene  is  treated  with  concen- 
trated nitric  acid,  or  with  a  mixture  of  nitric  and  sulphuric  acids, 
nitro-benzene  is  formed  : 

C6H6    +    HN03    :  :    C6H5NO2    +    H2O. 

Experiment  57.  Mix  50  c.c.  of  sulphuric  acid  with  25  c.c.  nitric  acid  ;  allow 
to  cool,  place  the  vessel  containing  the  mixture  in  water,  and  add  gradually  5 
c.c.  of  benzene,  waiting  after  the  addition  of  a  few  drops  each  time  until  the 
reaction  is  over.  Shake  well  until  all  benzene  is  dissolved  and  pour  the  liquid 
into  300  c.c.  of  water.  The  yellow  oil  which  sinks  to  the  bottom  is  nitro- 
benzene. It  may  be  purified  by  washing  with  water  and  redistilling,  after 
removal  of  water  and  shaking  with  calcium  chloride. 

Nitro-benzene  is  an  almost  colorless  or  yellowish  oily  liquid,  which 
is  insoluble  in  water,  has  a  specific  gravity  of  1.2,  a  boiling-point  of 
205°  C.  (401°  F.),  a  sweetish  taste,  highly  poisonous  properties,  even 


368 


CONSIDERATION  OF  CARBON  COMPOUNDS. 


when  inhaled,  and  an  odor  resembling  that  of  oil  of  bitter  almond, 
for  which  it  is  substituted  under  the  name  of  essence  ofmirbane.  It 
is  manufactured  on  a  large  scale  and  used  chiefly  in  the  preparation 
of  aniline,  for  which  see  Index. 

Benzene-derivatives.  The  relation  existing  between  methane- 
and  benzene-derivatives  may  be  shown  by  comparing  the  composition 
of  a  few  derivatives  : 


Methane,                       CH4 

Benzene, 

C6H6 

Methyl,                          CH3 

Benzyl, 
Phenyl, 

}C6H5 

Ethane                        }CH3.CH3 
Methyl-methane,       J 

Toluene, 
Methyl-benzene, 

}C6H5.CH3 

Methyl-hydroxide,    \  QJJ  QJJ 
Methyl-alcohol,          / 

Phenyl-hydroxide, 
Phenol, 

JC6H5.OH 

/OH 

/OH 

Glycerin,                       C3H5v-OH 

Pyrogallol, 

C6H3^-OH 

XOH 

VOH 

Acetic  acid,                   CH3.CO2H 

Benzoic  acid, 

C6H5.C02H 

Acetic  aldehyde,           CH3.COH 

Benzoic  aldehyde, 

C6H5.COH 

Ethyl-sulphonic  acid,  SO»  \Ajtj8 

Benzene-sulphonic 
acid, 

S°2\OH5 

/C*O  IT 
Malonic  acid,                 CH2^  pQ2TT 

Phtalic  acid, 

c^/cpji 

Tartaric  acid,                C2H2\2CO  H 

Salicylic  acid, 

c  H  /'OK 

Ethyl  ether,               j  {jj^/O 

Phenyl-ether, 

icX/° 

Methyl-ethyl  ether,  j  £  S3^)O 

v.  ^2      5^ 

Methyl-phenyl 
ether,  anisol, 

{c6I;)° 

The  following  graphic  formulas  may  serve  to  illustrate  the  consti- 
tution of  some  aromatic  compounds  : 

Alcohols. 
OH 


Hydrocarbons. 
H 


A 


C02H 


1 

C 


H 


A. 


Benzene,  C6H6. 


Phenol  or  carbolic  acid, 
C6H5.OH. 


Benzoic  acid,  C6H5.CO2H. 


H 


OH 

J, 


C02H 


\ 


H 


H 


A 


Nitro-benzene,  C6H6NOa. 


Resorcin,  C6H4(OH)2. 


XC02H 


\H 


Phtalic  acid,  C6H4(C02H)2. 


BENZENE  SERIES.    AROMATIC  COMPOUNDS.  369 

CH3  OH  OH 

H\     /<L        H  H  L         OIL         H  CvX     XOH 

\£J/       vQ/  ^C          ^C  ^C 


(I       /C\                          .Cv       /Cv  .Cv      /C. 

TTX        \.r\//         TT  TT^      Nf^-x      ^OH  H         ^C^^ 

H                                         H  CO2H 

Toluene,  methyl-benzene,  Pyrogallol,  C6H3(HO)3.  GaHic  acid,  C6H2.CO2H.(OH)3. 
C6H5.CH3. 

CH3                                      OH  OH 

/i                r^TT  TT                C*                r^TT  TT                I1                (Ti  TT 

"v^vx           ^v-'-tlfi  ^1\            >VA\           x^-^s  **\          /^<X         /V^W2J:I- 

\CX      ^CX 


H        ^  ^        ^  o     J 

vV  v  /,^-/ \  x^  \  X>>^\  v  ^  \  /s~*  * 


H 

Xylene,  di-methyl-benzene,  Cresol,  C6H4.CH3.OH.        Salicylic  acid, 

C6H5.(CH3)2. 

CH3  CH3  COH 

cj  d  '  A 


XCX    \H  Hx    \CX    ^OH         Hx    \C^    ^H 

C3H7  C3Hr  H 

Cymene,  methyl-propyl  benzene,    Thymol,  C6H3CH3.C8H7.OH.    Benzaldehyde,  oil  of  bitter 
C6H4.CH3.C3H7.  almond,  C6H5.COH. 

The  preceding  graphic  formulas  show  in  the  first  column  (besides 
nitro-benzene)  a  number  of  hydrocarbons,  in  the  second  column  alco- 
hols (or  phenols),  obtained  by  introducing  hydroxyl  into  the  hydro- 
carbon molecule,  and  in  the  third  column  chiefly  aromatic  acids, 
formed  by  introducing  carboxyl,  CO2H,  or  carboxyl  and  hydroxyl. 

Phenols.  While  the  term  phenol  is  generally  used  for  carbolic 
acid,  it  also  belongs  to  that  class  of  substances  which  we  may  call 
aromatic  alcohols.  According  to  the  number  of  hydrogen  atoms  re- 
placed by  hydroxyl,  we  find  mon-atomic,  di- atomic,  and  tri-atomic 
phenols,  corresponding  to  the  similarly  constituted  alcohols.  Phenols 
differ  from  common  alcohols  in  not  yielding  aldehydes  or  acids  by 
oxidation. 

Carbolic  acid,  Acidum  carbolicum,  C6H5OH  =  94  (Phenol, 
Phenyl  hydrate,  Phenyl  alcohol).  Crude  carbolic  acid  is  a  liquid 
obtained  during  the  distillation  of  coal-tar  between  the  temperatures 
of  170°-190°  C.  (338°-374°  F.),  and  containing  chiefly  phenol,  be- 

24 


370  CONSIDERATION  OF  CARBON  COMPOUNDS. 

sides  cresol,  C7H7OH,  and  other  substances.  It  is  a  reddish-brown 
liquid  of  a  strongly  empyrenmatic  and  disagreeable  odor. 

By  fractional  distillation  of  the  crude  carbolic  acid,  the  pure  acid 
is  obtained,  which  forms  colorless,  interlaced,  needle-shaped  crystals, 
sometimes  acquiring  a  pinkish  tint ;  it  has  a  characteristic,  slightly 
aromatic  odor,  is  deliquescent  in  moist  air,  soluble  in  from  15  to  20 
parts  of  water,  and  very  soluble  in  alcohol,  ether,  chloroform,  glycerin, 
fat  and  volatile  oils,  etc. ;  it  has,  when  diluted,  a  sweetish  and  after- 
ward burning,  caustic  taste;  it  produces  a  benumbing  and  caustic 
effect,  and  even  blisters  on  the  skin  ;  it  is  strongly  poisonous,  and  a 
powerful  antiseptic  agent,  preventing  fermentation  and  putrefaction 
to  a  marked  degree ;  fusing-point  about  35°  C.  (95°  F.),  boiling- 
point  188°  C.  (370°  F.),  specific  gravity  1.065. 

Phenol,  though  generally  called  carbolic  acid,  has  a  neutral  or  but 
faintly  acid  reaction,  and  the  constitution  of  an  alcohol,  but  it  readily 
combines  with  strong  bases,  for  instance,  with  sodium,  forming 
sodium  phenoxide  or  sodium  phenolate : 

C6H5OH     +    NaOH        =    C6H5ONa    +     H2O. 

Phenol  obtained  by  synthetical  processes  is  now  sold  in  a  state  of 
great  purity  ;  it  has  comparatively  little  odor. 

As  antidotes  may  be  used  olive  oil  or  castor  oil,  a  mixture  of  both,  or  a  mix- 
ture of  magnesia  and  oil. 

Tests  for  carbolic  acid. 

(Use  an  aqueous  solution.) 

1.  It  coagulates  albumin  and  collodion. 

2.  It  colors  solutions  of  neutral  ferric  chloride  intensely  and  per- 
manently violet-blue.     (Plate  VI.,  1.) 

3.  Bromine  water  produces,  even  in  dilute  solutions,  a  white  pre- 
cipitate of  tri-brom-phenol,  C6H2Br3OH. 

4.  A  fresh-cut  slip  of  pinewood  moistened  with  carbolic  acid,  and 
then  exposed  to  hydrochloric  acid  fumes,  turns  blue  on  exposure  to 
sunlight. 

5.  On  heating  with  nitric  acid  it  turns  yellow,  picric  acid  being 
formed. 

Creosote,  Creosotum.  This  is  a  liquid  product  of  the  distilla- 
tion of  wood-tar,  especially  of  beechwood-tar,  which  contains  some- 
times as  much  as  25  per  cent,  of  creosote ;  it  resembles  carbolic  acid 
in  many  respects,  especially  in  its  antiseptic  properties  and  its  action 


PLATE    VI. 


BENZENE    DERIVATIVES. 


Carbolic  acid  with  ferric  chloride. 


Salicylic   acid  with   ferric  chlo- 
ride. 


Pyrogallic    acid    with    alcoholic 
solution  bf  potassium  hydroxide. 


Gallotannic  acid,  precipitated  by 

ferric   chloride    and    precipitate   dis- 
solved in  excess  of  tannic  acid. 


Santonin  with  alcoholic  solution 
of  potassium  hydroxide. 


Acetaiiilid  treated  successively 
with  hydrochloric  acid,  carbolic  acid, 
bleaching  powder,  and  ammonia  water. 


Aiitipyrine    treated    with    nitric 
acid. 


Aiitipyrine  with  solution  of  sodi- 
um nitrite  and  acetic  acid. 


BENZENE  SERIES.     AR  OMA  TIC  COMPO  UNDS.  371 

on  the  skin.     It  is  a  mixture  of  substances,  but  consists  chiefly  of 
creosol,  C8H10O2,  and  guaiacol,  C7H8O2. 

From  carbolic  acid  creosote  may  be  distinguished  by  not  coagulat- 
ing albumin  and  collodion,  by  not  being  solidified  on  cooling,  by  not 
coloring  ferric  chloride  permanently,  and  by  its  boiling-point,  which 
rises  from  205°  to  215°  C.  (401°  to  419°  F.). 

Sulphocarbolic  acid,  HSO3.C6H4.OH  (Phenol-sulphonic  .acid, 
Sozolic  acid,  Aseptol).  Formed  by  dissolving  carbolic  acid  in  strong 
sulphuric  acid : 

C6H5OH    4-    H2S04    :       HC6H5SO4    4-    H2O. 

Sodium  Sulphocarbolate,  Sodii  sulphocarbolas,  NaSO3.C6H4.OH  + 
21^0,  is  obtained  as  a  white  soluble  salt  by  dissolving  sodium  car- 
bonate in  the  above  acid. 

Sulphonic  acid  has  been  spoken  of  before,  when  it  was  shown  that  mercap- 
tans  are  converted  into  compounds  termed  sulphonic  acids.  These  acids  may 
be  looked  upon  as  derivatives  of  sulphurous  acid,  obtained  from  it  by  replace- 
ment of  hydrogen  by  radicals.  The  relation  existing  between  carbonic  and 
sulphonic  acids  may  be  represented  by  the  following  formulas  : 

Carbonic  acid,  CO^QH  Sulphuric  acid,  S^  X°H 


Formic  acid,  CO\QH  Sulphurous  acid,  S^  ' 

xOTT 

Acetic  acid,  CO^  QJJS  Methyl-sulphonic  acid,  S 

^arboTa^d,         CO<OH  Any  sulphonic  acid,       S 

According  to  this  view,  the  above  sulphocarbolic  acid  is  actually  phenol- 

./f  TT  O 

sulphonic  acid,  its  constitution  being  represented  by  the  formula,  SO.X  0Vr 5    . 

Ichthyol,  Sodium  ichthyo-sulphonate,  C^H^Na-jOg.  Ichthyol  is  the  sodium  or 
ammonium  salt  of  a  complex  sulphonic  acid,  obtained  by  the  dry  distillation 
of  a  bituminous  mineral  found  in  Tyrol.  It  is  a  brown,  tar-like  liquid,  having 
a  disagreeable  odor. 

Picric  acid,  C6H2(NO2)3OH  ( Trinitro- phenol,  Carbazotic  acid).  This 
substance  is  formed  by  the  action  of  nitric  acid  on  various  matters 
(silk,  wool,  indigo,  Peruvian  balsam,  etc.),  and  is  manufactured  on  a 
large  scale  by  slowly  dropping  carbolic  acid  into  fuming  nitric  acid. 
Picric  acid  forms  yellow  crystals,  which  are  sparingly  soluble  in 
water ;  it  has  a  very  bitter  taste,  strongly  poisonous  properties,  and  is 
used  as  a  yellow  dye  for  silk  and  wool,  and  as  a  reagent  for  albumin. 
While  carbolic  acid  has  but  slight  acid  properties,  picric  acid  behaves 


372  CONSIDERATION  OF  CARBON  COMPOUNDS. 

like  a  strong  acid,  forming  salts  known  as  picrates,  most  of  which  are 
explosive. 

Phenacetin,  Para-acetphenetidin,  C6H4.0(C2H3)  .NH(C2H30) .  When  mono- 
nitrophenol,  C6H4.NO2.OH,  is  treated  with  reducing  agents,  the  oxygen  of 
N02  is  replaced  by  hydrogen,  and  amido-phenol,  C6H4.OH.NH2,  is  formed. 
The  methyl  ether  of  this  compound,  C6H4.O(CH;j).NH2,  is  known  as  anisidin, 
and  the  ethyl  ether,  C6H4.O(C2H5).NH.,,  as  phenetidin.  By  the  action  of  glacial 
acetic  acid  upon  para-phenetidin,  one  hydrogen  atom  in  NH2  is  replaced  by 
acetyl,  C2H3O,  when  para-acetphenetidin  is  formed.  The  compound  is  used  as 
an  antipyretic  under  the  name  of  phenacetin. 

It  is  a  colorless,  odorless,  tasteless  powder,  sparingly  soluble  in  water,  readily 
soluble  in  alcohol ;  it  fuses  at  135°  C.  (275°  F.).  Fresh  chlorine  water  colors  a 
hot  aqueous  solution  first  violet,  then  ruby-red.  The  same  color  is  obtained  by 
boiling  0.1  gramme  of  phenacetin  with  1  c.c.  of  hydrochloric  acid  for  one 
minute,  diluting  with  10  c.c.  of  water,  filtering  when  cold,  and  adding  3  drops 
of  solution  of  chromic  acid. 

Resorcin,  Resorcinum,  C6H4(OH)2  (Resorcinol,  Meta-dihydroxy- 
benzene).  The  formula  indicates  that  this  compound  is  a  di-atomic 
phenol.  It  is  formed  by  fusing  different  resins,  such  as  galbanum, 
asafoetida,  etc.,  with  caustic  alkalies,  but  it  is  also  obtained  syntheti- 
cally from  benzene. 

Resorcin  is  a  white,  or  faintly-reddish,  crystalline  powder,  having  a  some- 
what sweetish  taste  and  a  slightly  aromatic  odor;  it  fuses  at  118°  C.  (244°  F.), 
boils  at  276°  C.  (529°  F.),  and  is  soluble  in  less  than  its  own  weight  of  water. 
A  dilute  solution  gives  with  ferric  chloride  a  bluish- violet  color.  Resorcin, 
when  heated  for  a  few  minutes  with  phtalic  acid  in  a  test-tube,  forms  a 
yellowish-red  mass,  which,  when  added  to  a  dilute  solution  of  caustic  soda, 
forms  a  highly  fluorescent  solution.  Other  fluorescent  compounds  are  obtained 
by  heating  resorcin  with  very  little  sulphuric  and  either  citric,  oxalic,  or 
tartaric  acid,  dissolving  in  a  mixture  of  water  and  alcohol  and  supersaturating 
the  solution  with  ammonia.  Resorcin  is  largely  used  in  the  manufacture  of 
certain  dyes. 

Cymene,  C10H14  or  C6H4.CH3.C3H7  (Para-mdhyl-propyl-benzene). 
This  hydrocarbon  occurs  in  the  oil  of  thyme  and  in  the  volatile  oils 
of  a  few  other  plants ;  it  has  also  been  made  synthetically ;  it  is  a 
liquid  of  a  pleasant  odor,  boiling  at  175°  C.  (347°  F.). 

Cymene  is  of  special  interest,  because  it  is  closely  related  to  the 
terpenes  and  camphors,  from  all  of  which  it  may  be  obtained  by 
comparatively  simple  processes. 

Terpenes,  C10H16.  This  term  is  applied  to  the  various  isomeric 
hydrocarbons  of  the  composition  C10H16,  which  are  often  looked  upon 
as  compounds  formed  by  direct  addition  of  hydrogen  to  cymene. 


BENZENE  SERIES.     AROMATIC  COMPOUNDS.  373 

Terpenes  are  the  chief  constituents  of  a  large  number  of  essential 
oils,  such  as  oil  of  turpentine,  juniper,  lemon,  rosemary,  bergamot, 
lavender,  etc.  Terpenes  are  readily  acted  upon  by  many  agents,  and 
hence  undergo  numerous  changes.  One  of  these  changes  is  polymeri- 
zation— i.  e.,  conversion  into  compounds  of  the  composition  C15H24 
and  C20H32,  which  may  be  eifected  by  heating  a  terpene  in  a  sealed 
tube,  or  by  shaking  it  with  concentrated  sulphuric  acid  or  with 
certain  other  substances.  Oxygen  and  hydrochloric  acid  combine 
directly  with  terpeues ;  dilute  nitric  acid  oxidizes  them  readily  with 
the  formation  of  a  number  of  organic  acids ;  bromine  and  iodine 
convert  them  into  cymene. 

Oil  of  turpentine ,  C10H16,  is  the  terpene  most  largely  used.  It  is  a 
thin,  colorless  liquid  of  a  characteristic  aromatic  odor,  and  an  acrid, 
caustic  taste;  it  is  insoluble  in  water,  soluble  in  alcohol,  and  an  excel- 
lent solvent  for  resins  and  many  other  substances.  When  treated 
with  hydrochloric  acid  gas  direct  combination  takes  place  and  a 
white  solid  substance  of  the  composition  C10H16HC1  is  formed,  which 
is  known  as  terpene  hydrochloride,  or  artificial  camphor,  on  account 
of  its  similarity  to  camphor  both  in  appearance  and  odor. 

Experiment  58.  Through  10  or  20  c.c.  of  oil  of  turpentine  pass  a  current  of 
hydrochloric  acid  gas  for  some  time,  or  until  a  quantity  of  a  solid  substance  has 
separated.  Collect  this  substance,  which  is  artificial  camphor,  upon  a  filter ; 
notice  its  characteristic  odor.  Heat  some  of  it ;  hydrochloric  acid  is  set  free. 

Terebene,  C10H16,  is  the  optically  inactive  modification  of  terpene,  obtained 
from  oil  of  turpentine  by  mixing  it  with  sulphuric  acid,  distilling,  washing 
the  distilled  oil  with  soda  solution,  redistilling  and  collecting  the  portions 
which  pass  over  at  a  temperature  of  156°  to  160°  C.  (313°  to  320°  F.).  Terebene 
resembles  oil  of  turpentine  in  most  respects,  but  has  not  the  unpleasant  odor  of 
this  oil. 

Resins  are  obtained,  together  with  the  essential  oils,  from  plants. 
Mixtures  of  a  resin  and  a  volatile  oil  are  known  as  oleo-resins,  while 
mixtures  of  a  resin  or  oleo-resins  and  gum  are  known  as  gum-resins. 
The  name  balsam  is  also  used  for  a  certain  group  of  oleo-resins. 

The  resins  are  mostly  amorphous,  brittle  bodies,  insoluble  in  water, 
but  soluble  in  alcohol,  ether,  fatty  and  essential  oils  ;  they  are  fusible, 
but  decompose  before  being  volatilized  ;  they  all  contain  oxygen  and 
exhibit  somewhat  acid  properties. 

Turpentine,  the  oleo-resin  of  the  conifers,  contains  besides  the  oil  of 
turpentine  a  resin  called  colophony,  rosin,  or  ordinary  resin,  consisting 
chiefly  of  the  anhydride  of  abietic  acid,  C44H64O5. 


374  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Copaiva  balsam  consists  of  a  volatile  oil  and  a  resin,  the  latter 
being  principally  copaivic  acid,  C20H30O2. 

Of  fossil  resins  may  be  mentioned  amber  and  asphalt,  the  latter 
having  most  likely  been  formed  from  petroleum. 

India-rubber,  Blastica  (Caoutchouc),  is  the  dried  milky  juice  found 
in  quite  a  number  of  trees  growing  in  the  tropics.  The  principal 
constituents  are  hydrocarbons  of  the  composition  C20H32,  CIOH16,  and 
C5H8.  The  commercial  article  is  yellowish-brown,  has  a  specific 
gravity  of  0.92  to  0.94,  is  soft,  flexible,  insoluble  in  water  and  alcohol, 
but  soluble  in  carbon  disulphide,  ether,  chloroform,  and  benzene.  It 
is  not  acted  upon  by  dilute  mineral  acids ;  concentrated  nitric  and 
sulphuric  acid,  as  well  as  chlorine,  attack  it  after  a  time.  It  is  hard 
and  tough  in  the  cold;  when  heated  it  becomes  viscous  at  125°  C. 
(257°  F.),  and  fuses  at  170°-180°  C.  (347°-356°  F.)  to  a  thick  liquid, 
which,  on  cooling,  remains  sticky,  and  only  regains  its  original  char- 
acter after  a  long  time. 

Vulcanized  rubber  is  india-rubber  which  has  been  caused  to  enter 
into  combination  with  from  7  to  10  per  cent,  of  sulphur  by  heating 
together  the  two  substances  to  a  temperature  of  130°-150°  C.  (266°- 
302°  F.).  Vulcanized  rubber  differs  from  the  natural  article  by 
possessing  greater  elasticity  and  flexibility,  by  resisting  the  action  of 
solvents,  reagents  and  atmosphere  to  a  higher  degree,  and  by  not 
hardening  when  exposed  to  cold. 

Hard  rubber,  vulcanite,  or  ebonite,  is  vulcanized  rubber,  containing 
from  20  to  35  per  cent,  of  sulphur,  and  often  also  tar,  white-lead, 
chalk,  or  other  substances.  It  is  hard,  tough,  and  susceptible  of  a 
good  polish. 

Gutta-percha  is  the  concrete  juice  of  a  tree — Isonandra  gutta.  It 
resembles  india-rubber  both  in  composition  and  properties.  At  ordi- 
nary temperature  it  is  a  yellowish  or  brownish,  hard,  somewhat 
flexible,  but  scarcely  elastic  substance ;  when  warmed  it  softens,  and 
is  plastic  above  60°  C.  (140°  F.) ;  at  the  temperature  of  boil  ing- water 
it  is  very  soft.  It  is  insoluble  in  water,  alcohol,  dilute  acids  and 
alkaline  solutions ;  soluble  in  oil  of  turpentine,  carbon  disulphide 
and  chloroform. 

Stearoptens  or  Camphors  are  substances  closely  related  to  the 
terpenes  and  to  cymene  both  in  physical  and  chemical  properties ; 
while  terpenes  are  liquids,  camphors  are  crystalline  solids.  Borneo 


BENZENE  SERIES.     AROMATIC  COMPOUNDS.  375 

camphor  has  the  composition  C10H18O,  while  the  camphor  found 
in  the  camphor-trees  of  China  and  Japan  has  the  composition 
C10H160. 

Camphor,  Camphora,  C10H16O  (Laurinol),  forms  white,  translucent 
masses  of  a  tough  consistence  and  a  crystalline  structure ;  it  has  a 
characteristic,  penetrating  odor  and  poisonous  properties;  in  the 
presence  of  a  little  alcohol  or  ether  it  may  be  pulverized ;  it  is  nearly 
insoluble  in  water,  but  soluble  in  alcohol,  ether,  chloroform,  etc. ; 
boiled  with  bromine  it  forms  the  monobromated  camphor,  C10H15BrO, 
of  the  U.  S.  P.,  a  white  crystalline  substance  having  a  mild  cam- 
phoraceous  odor  and  taste.  Heating  with  nitric  acid  converts  cam- 
phor into  camphoric  acid,  C8H14(CO2H)2,  a  colorless,  crystalline, 
fusible  substance,  having  an  acid  taste ;  it  is  slightly  soluble  in  water, 
readily  in  alcohol  and  ether. 

Menthol,  C10H19OH  (Mint-camphor}.  Found  together  with  a 
terpene  in  oil  of  peppermint,  and  separates  in  crystals  on  cooling  the 
oil.  Menthol  is  nearly  insoluble  in  water,  fuses  at  43°  C.  (109°  F.) 
and  boils  at  212°  C.  (414°  F.).  It  has  the  characteristic  odor  of 
peppermint. 

Thymol,  C10H14O  or  C6H3.CH3.C3H7.OH  (Methyl-propylphenol). 
Thymol  is  found  in  small  quantities  as  a  constituent  of  the  volatile 
oils  of  wild  thyme,  horse-mint,  and  a  few  other  plants. 

Thymol  crystallizes  in  large  translucent  plates,  has  a  mild  odor,  a  warm, 
pungent  taste,  melts  at  50°  C.  (122°  F.)  and  boils  at  230°  C.  (446°  F.)  It  is  now 
largely  used  as  an  excellent  and  very  valuable  antiseptic,  preference  being 
given  to  it  on  account  of  its  comparative  harmlessness  when  compared  with 
the  strongly  poisonous  carbolic  acid. 

Thymol  dissolved  in  moderately  concentrated  warm  solution  of  potassium 
hydroxide,  gives  on  the  addition  of  a  few  drops  of  chloroform  a  violet  color, 
which  on  heating  soon  changes  into  a  beautiful  violet-red. 

Eucalyptol,  C10H180,  is  found  in  the  volatile  oils  of  different  species  of 
eucalyptus,  as  also  in  the  oils  of  some  other  plants.  It  is  liquid  at  the  ordinary 
temperature,  but  solidifies  when  cooled  to  a  little  below  the  freezing-point.  It 
has  an  aromatic,  distinctly  camphoraceous  odor. 

Benzole  acid,  Acidum  benzoicum,  HC7H5O2  or  C6H5CO2H  = 
122.  Found  in  benzoin  and  some  other  resins  ;  also  in  combination 
with  other  substances  in  the  urine  of  herbivorous  animals;  it  is 
obtained  from  benzoin  by  heating  it  carefully,  when  the  volatile 
benzoic  acid  sublimes.  It  is  now  also  manufactured  from  toluene, 


376  CONSIDERATION  OF  CARBON  COMPOUNDS. 

which  is  first  converted  into  ben zo- trichloride  (trichlormethyl-ben- 
zene)  by  passing  chlorine  into  hot  toluene : 

C6H5CH3    -f     6C1       :    C6H5CC13     +    3HC1. 

Benzo-trichloride,  when  treated  with  water  under  pressure,  yields 
benzoic  and  hydrochloric  acids,  thus : 

C6H5CC13    +    2H20    :   :    C6H5CO2H    +    3HC1. 

Benzoic  acid  forms  white,  lustrous  scales  or  friable  needles,  having  a 
slight  aromatic  odor  of  benzoin,  and  an  acid  reaction;  it  is  but 
slightly  soluble  in  cold  water,  but  easily  soluble  in  alcohol,  ether, 
oils,  etc. 

Benzoic  acid,  when  neutralized  with  an  alkali,  gives  a  flesh-colored 
or  reddish  precipitate  of  ferric  benzoate  on  the  addition  of  a  neutral 
solution  of  ferric  chloride. 

By  neutralizing  benzoic  acid  with  either  ammonium  hydroxide, 
sodium  hydroxide,  or  lithium  carbonate,  the  official  salts  ammonium 
benzoate,  NH4C7H5O2,  sodium  benzoate,  NaC7H5O2.H2O,  and  lithium 
benzoate,  LiC7H5O2,  are  obtained.  The  three  salts  are  white,  soluble 
in  water,  and  have  a  slight  odor  of  benzoin. 

Oil  of  bitter  almond,  Oleum  amygdalae  amarse,  C7H6O  or 
C6H5COH  (Benzaldehyde).  As  shown  by  the  formula,  oil  of  bitter 
almond  differs  from  benzoic  acid  in  containing  one  atom  less  of 
oxygen ;  in  all  its  reactions  it  behaves  like  a  true  aldehyde,  being, 
for  instance,  easily  converted  into  benzoic  acid  by  oxidation. 

It  does  not  occur  in  a  free  state  in  nature,  but  is  formed  by  a 
peculiar  fermentation  of  a  glucoside,  amygdalin,  existing  in  bitter 
almonds,  in  cherry-laurel,  and  in  the  kernels  of  peaches,  cherries, 
etc.,  but  not  in  sweet  almonds.  The  ferment  causing  the  decomposi- 
tion of  amygdalin  is  a  substance  termed  emulsine,  which  is  found  in 
both  bitter  and  sweet  almonds.  As  water  is  required  for  the  decom- 
position, the  emulsine  does  not  act  upon  the  amygdalin  contained  in 
the  same  seed  until  water  is  added,  when  the  decomposition  takes 
place  as  follows : 

C20H27NOn    +     2H20    =    2C6H12O6    +     HCN     +     CTH6O. 
Amygdalin.  Water.  Glucose.         Hydrocyanic      Oil  of  bitter 

acid.  almond. 

The  oil  is  obtained  by  maceration  of  bitter  almonds  with  water, 
and  subsequent  distillation  when  it  distils  over  with  hydrocyanic 
acid  and  steam,  and  separates  as  a  heavy  oil  in  the  distillate. 

It  is  an  almost  colorless,  thin  liquid  of  a  characteristic  aromatic 


BENZENE  SERIES.    AROMATIC  COMPOUNDS.  377 

odor,  a  bitter  and  burning  taste,  and  a  neutral  reaction.  The  pure 
oil  is  not  poisonous,  but  the  crude  oil  of  bitter  almond  is  poisonous 
on  account  of  its  containing  hydrocyanic  acid. 

Bitter  almond  water,  Aqua  amygdalae,  amarce,  is  made  by  dissolving 
1  part  of  the  oil  in  999  parts  of  water. 

Salicylic  acid,  Acidum  salicylicum,  HC7H5O3  or  C6H4OH.CO2H 
=  138.  Derived  from  benzene  by  introducing  one  hydroxyl  and 
one  carboxyl  radical.  It  is  found  in  several  species  of  violet,  and  in 
the  form  of  methyl  salicylate  in  the  wintergreen  oil  (oil  of  Gaul- 
theria  procumbens).  May  be  obtained  by  fusing  potassium  hydroxide 
with  salicin. 

Salicylic  acid  is  manufactured  from  carbolic  acid  by  passing  carbon  dioxide 
through  sodium  carbolate  (sodium  phenoxide),  when  sodium  salicylate  remains 
and  carbolic  acid  distils  over  : 

C6H5OH     +     NaOH    =     C6H5ONa     4-     H2O. 
Carbolic  acid.          Sodium  Sodium 

hydroxide.  carbolate. 

2(C6H5ONa)     +     C02    =    C6H4NaOCO2Na     +     C6H5OH. 

Sodium  Carbon  Sodium  salicylate.  Carbolic 

carbolate.  dioxide.  acid. 

Sodium  salicylate,  thus  obtained,  is  decomposed  by  hydrochloric  acid  : 


a     +     2HC1        :    C6H4OHCO2H     +     Nad 
Sodium  salicylate.         Hydrochloric         Salicylic  acid.  Sodium 

acid.  chloride. 

Salicylic  acid  is  a  white,  solid,  odorless  substance,  having  a 
sweetish,  slightly  acrid  taste,  and  an  acid  reaction  ;  it  is  but  sparingly 
soluble  in  cold  water,  but  readily  soluble  in  alcohol,  ether,  etc.  ;  it 
fuses  at  about  157°  C.  (315°  F.),  and  sublimes  at  200°  C.  (392°  F.). 
It  is  a  valuable  antiseptic. 

By  dissolving  the  alkali  hydroxides  in  salicylic  acid,  the  various 
salts  may  be  obtained,  as,  for  instance,  sodium  salicylate,  NaC7H5O3, 
and  lithium  salicylate,  LiC7H5O3,  both  of  which  are  white,  soluble 
salts. 

Analytical  reactions. 

1.  Add  to  solution  of  salicylic  acid  or  its  salts  ferric  chloride  :  a 
reddish-violet  color  is  produced,  yet  noticeable  in  solutions  containing 
1  part  of  salicylic  acid  in  500,000  parts  of  water.     (Plate  VI.,'2.) 

2.  Add  some  cupric  sulphate  :  a  bright-green  color  will  result. 

3.  Dissolve  some  salicylic  acid  or  sodium  salicylate  in    methyl 
alcohol  and  add   one-fourth  the  volume  of  sulphuric  acid.     Heat 


378  CONSIDERATION  OF  CARBON  COMPOUNDS. 

gently  and  set  aside  for  a  few  minutes.     On  reheating,  the  odor  of 
methyl  salicylate  is  developed. 

Salicin,  C13H1807.  This  glucoside  is  found  in  several  species  of  Salix  (willow), 
and  is  mentioned  here  because  it  splits  into  glucose  and  salicylic  alcohol, 
C6H4.OH.CH2OH,  when  boiled  with  dilute  acids  : 

C13H1807  +  H20  =  C6H120  +  C7H802. 

Salicylic  alcohol  is  converted  by  chromic  acid  into  salicylic  aldehyde,  C6H4 
OH.COH,  which  by  further  oxidation  is  converted  into  salicylic  acid. 

Salicin  forms  white,  silky,  shining  needles,  which  are  soluble  in  less  than  an 
equal  weight  of  water,  have  a  neutral  reaction  and  a  very  bitter  taste. 

Salicin  sprinkled  upon  concentrated  sulphuric  acid  produces  a  red  color. 
Boiled  with  very  dilute  hydrochloric  acid  for  a  few  minutes,  and  this  solution 
nearly  neutralized  with  sodium  carbonate,  a  violet  color  is  produced  on  the 
addition  of  a  drop  of  ferric  chloride  solution. 

Methyl  salicylate,  CH3.C7H503.  Oil  of  wintergreen  is  chiefly  methyl  sali- 
cylate, a  nearly  colorless  liquid  with  a  characteristic,  strongly  aromatic  odor. 
It  is  made  by  the  method  so  extensively  used  in  the  manufacture  of  compound 
ethers,  viz.,  by  heating  of  salicylic  acid  with  methyl  alcohol  in  the  presence  of 
sulphuric  acid.  (See  above  reaction  3  of  salicylic  acid.) 

Phenyl  salicylate,  Salol,  C6H5.C7H5O3.  This  compound  ether  is 
a  white,  crystalline,  tasteless  powder,  which  is  nearly  insoluble  in 
water,  readily  soluble  in  alcohol,  ether,  and  benzol,  and  fuses  at  42° 
C.  (107.4°  F.).  It  is  used  as  an  antiseptic  and  antipyretic. 

Salol  heated  with  potassium  hydroxide  solution  causes  its  decom- 
position into  phenol,  which  can  be  recognized  by  its  odor,  and  potas- 
sium salicylate,  from  which  crystalline  salicylic  acid  will  separate 
upon  supersaturating  the  liquid  with  hydrochloric  acid.  An  excess 
of  bromine-water  produces  a  white  precipitate  in  an  alcoholic  solution 
of  salol. 

Salol  is  made  by  the  action  of  suitable  dehydrating  agents  upon  a 
mixture  of  phenol  and  salicylic  acid  : 

C6H5OH  +  HC7H503  =  C6H5.C7H503  +  H2O. 

Phtalic  acid,  C6H4.(C02H)2,  is  a  dibasic  acid,  which,  when  heated,  loses 
water,  and  is  converted  into  phtalic  anhydride  : 

C6H4.(C02H)2    :   :    H20     +     C6H4C203. 

The  latter  compound,  when  treated  with  phenol  in  the  presence  of  sulphuric 
acid,  forms  phenol-phtalein: 

2C6H60     +     C8H403    =    H20     +     C20H1404. 
Phenol.      Phtalic  anhydride.  Phenol-phtalein . 

A  solution  of  phenol-phtalein  shows  a  purplish-red  color  in  the  presence  of 
alkalies ;  this  color  is  destroyed  by  acids.  This  property  is  made  use  of  in 
alkalimetry,  where  phenol-phtalein  serves  as  an  indicator. 


BENZENE  SERIES.     AROMA  TIC  COMPO  UNDS.  379 

Gallic  acid,  Acidum  gallicum,  HC7H5O5,  or  C6H2(OH)3.CO.iH  = 
17O.  Obtained  by  exposing  moistened  nut-galls  to  the  air  for  about 
six  weeks,  when  a  peculiar  fermentation  takes  place,  during  which 
tannic  acid  is  converted  into  gallic  acid,  which  is  purified  by  crystal- 
lization. The  crystals  contain  one  molecule  of  water,  which  may  be 
expelled  at  100°  C.  (212°  F.).  It  is  a  white,  solid  substance,  forming 
long,  silky  needles ;  it  has  an  astringent  and  slightly  acidulous  taste, 
and  an  acid  reaction  ;  it  is  soluble  in  about  100  parts  of  cold  or  in  3 
parts  of  boiling  water,  also  readily  soluble  in  alcohol,  but  sparingly 
in  ether  and  chloroform;  it  gives  a  bluish-black  precipitate  with 
ferric  salts,  and  does  not  coagulate  albumin,  nor  precipitate  alkaloids, 
gelatin,  or  starch.  A  piece  of  potassium  cyanide  added  to  solution 
of  gallic  acid  produces  a  deep  rose  color. 

Pyrogallol,  Pyrog-allic  acid,  C6H3.(OH)3.  When  gallic  acid  is 
heated  to  200°  C.  (392°  F.)  it  is  decomposed  into  carbon  dioxide  and 
pyrogallol,  a  substance  which  is  not  a  true  acid,  but  tri-hydroxy- 
benzene,  i.  e.y  a  tri -atomic  phenol.  Pyrogallol  crystallizes  in  color- 
less needles,  melts  at  131°  C.  (268°  F.),  is  easily  soluble  in  water, 
ether,  and  alcohol.  In  alkaline  solution  it  absorbs  oxygen  rapidly, 
assuming  a  red,  then  reddish-brown  and  dark-brown  color  (Plate 
VI.,  3).  Nitric  acid  also  colors  it  yellow,  then  brown,  and  this 
property  is  made  use  of  in  testing  for  traces  of  nitric  acid.  Solutions 
of  silver,  gold,  and  mercury  are  reduced  by  pyrogallol  even  in  the 
cold. 

Tannic  acid,  Acidum  tannicum,  HC14H9O9  =  322  (Gallotannic 
acid,  Digallic  acid).  There  are  a  number  of  tannic  acids,  or  tannins, 
found  in  various  parts  of  different  plants  (oak-bark,  nut-galls,  cin- 
chona, coffee,  tea,  etc.),  the  properties  of  which  are  not  quite  identical. 
All  tannins,  however,  are  amorphous,  have  a  faint  acid  reaction  and 
strongly  astringent  properties  ;  they  all  precipitate  albumin  and  most 
of  the  alkaloids ;  they  give  with  ferric  salts  a  dark-colored  solution 
or  precipitate,  the  color  being  dark  green  or  dark  blue ;  they  form 
with  animal  substances  compounds  which  do  not  putrefy.  Use  is 
made  of  this  property  in  the  process  of  tanning — i.  e ,  converting 
hides  into  leather. 

The  official  or  gallotannic  acid  is  obtained  by  extracting  nut-galls 
with  ether  and  alcohol,  and  evaporating  the  solution  ;  it  forms  light- 
yellowish,  amorphous  scales,  having  a  faint  and  characteristic  odor, 
a  strongly  astringent  taste  and  an  acid  reaction  ;  it  is  easily  soluble 
in  water  and  diluted  alcohol. 


380  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Analytical  reactions  : 

1.  To  solution  of  tannic  acid  add  ferric  chloride  :  a  blue-black 
precipitate  falls,  soluble  in  large  excess  of  tannic  acid  with  violet 
color  (Plate  VI.,  4).     If  ferric  chloride  is  added  in  excess,  the  black 
precipitate  dissolves  in  it  with  green  color. 

2.  Add  a  few  drops  of  potassium  hydroxide  :  a  brown  coloration 
results. 

3.  To  a  dilute  solution  (1  in  100)  of  tannic  acid  add  gradually 
lime-water.     A  white  precipitate  falls,  which  on  addition  of  more 
lime-water  becomes  blue  by  reflected,  green  by  transmitted  light,  and 
darkens  by  exposure  to  air. 

4.  Tannic  acid  precipitates  solutions  of  gelatin,  albumin,  gelatinized 
starch,  tartar  emetic,  and  most  of  the  alkaloids. 

Naphtalin,  C10H8  (Naphtalene).  The  constitution  of  all  benzene- 
derivatives  considered  so  far,  may  be  explained  by  the  introduction 
of  radicals  in  benzene.  Naphtalin  and  its  derivatives  must  be 
assumed  to  be  formed  by  the  union  of  two  benzene  residues  in  such 
a  way  that  they  have  two  carbon  atoms  in  common,  as  represented  in 
these  formulas  : 

H         H  H          OH 

c 


H/   ^O/   W   \H  H/C^C/CWC\H 

i    i  A:    4 

Naphtalin,  C10H8.  Naphtol,  QoH^OH. 

Naphtalin  has  been  mentioned  as  a  product  of  the  destructive  distillation 
of  coal,  and  is  obtained  from  that  portion  of  coal-tar  which  boils  between  180° 
and  220°  C.  (356°  and  428°  F.).  This  distillate  is  treated  with  caustic  soda  and 
then  with  sulphuric  acid  and  distilled  with  water  vapor. 

When  pure,  naphtalin  forms  colorless,  lustrous  crystalline  plates,  having  a 
penetrating  but  not  unpleasant  odor  and  a  burning,  aromatic  taste.  It  fuses 
at  80°  C.  (176°  F.),  and  boils  at  218°  C.  (424°  F.),  but  volatilizes  slowly  at 
ordinary  temperature,  and  readily  with  water  vapor.  It  is  only  sparingly 
soluble  in  water,  but  easily  soluble  in  alcohol,  ether,  chloroform,  etc.  Impure 
naphtalin  assumes,  when  exposed  to  light,  a  reddish  or  brownish  color.  Naph- 
talin is  converted  into  phtalic  acid  by  oxidizing  agents. 

Naphtol,  C10H7OH.  This  compound  bears  to  naphtalin  the  same 
relation  as  phenol  to  benzene  —  i.  e.,  hydroxyl  replaces  hydrogen  in 
the  respective  hydrocarbons.  Two  isomeric  naphtols  are  known, 


BENZENE  SERIES.    AROMATIC  COMPOUNDS.  381 

which  differ  in  their  physical  properties  and  in  their  physiological 
action.  The  uaphtol  which  is  used  medicinally  is  chiefly  beta-naphtol, 
a  solid  compound  crystallizing  in  thin,  shining  plates,  having  an  odor 
similar  to  phenol  and  a  burning,  acrid  taste.  It  fuses  at  122°  C. 
(252°  F.),  boils  at  286°  C.  (547°  F.),  is  insoluble  in  about  1000  parts 
of  cold  or  75  parts  of  boiling  water ;  and  readily  soluble  in  alcohol, 
ether,  chloroform,  and  fatty  oils.  The  aqueous  solution  is  colored 
green  by  ferric  chloride.  Naphtol  is  found  in  coal-tar,  but  is  usually 
prepared  from  naphtalin. 

Santonin,  C15H18O3.  Although  many  efforts  have  been  made  to 
disclose  the  constitution  of  santonin,  and  though  many  derivatives  of 
it  have  been  formed,  we  know  as  yet  but  little  of  its  structure,  but 
it  may  be  the  anhydride  of  santonic  acid,  C15H20O4.  As  several  re- 
actions point  to  a  relationship  between  santonin  and  naphtalin,  it  is 
mentioned  in  this  place. 

Santonin  is  the  active  principle  of  wormseed,  the  unexpanded 
flowerheads  of  Artemisia,  from  which  it  is  obtained  by  extraction 
with  alcohol  and  lime-water,  and  decomposition  of  the  soluble  com- 
pound of  lime  and  santonin  by  an  acid.  Santonin  crystallizes  in 
colorless  prisms,  which  turn  yellow  on  exposure  to  light ;  it  is  but 
sparingly  soluble  in  water,  more  soluble  in  alcohol  and  ether. 

Santonin  taken  internally  confers  upon  the  urine  a  dark  color  re- 
sembling the  color  of  urine  containing  bile ;  upon  heating  such  urine 
it  turns  cherry-red  or  crimson,  the  color  disappearing  on  the  addition 
of  an  acid,  and  reappearing  on  neutralization. 

Analytical  reactions : 

1.  Santonin  added  to  alcoholic  solution  of   potassium  hydroxide 
produces   a   bright-red   liquid   which   gradually  becomes  colorless. 
(Plate  VI.,  5.) 

2.  To  1  c.c.  of  sulphuric  acid  add  a  few  drops  of  ferric  chloride 
solution  and  a  crystal  of  santonin  :  on  heating,  a  dark-red  color  is 
produced,  changing  into  violet-brown. 


QUESTIONS. — 471.  What  is  the  difference  between  fatty  and  aromatic  com- 
pounds, and  from  which  two  hydrocarbons  are  they  derived  ?  472.  From  what 
source  is  benzene  obtained,  how  can  it  be  made  from  benzoic  acid,  and  what 
are  its  properties?  473.  Give  the  graphic  formulas  of  benzene,  nitro-benzene, 
cymene,  phenol,  thymol,  benzoic  acid,  and  salicylic  acid.  Mention  methane 
derivatives  which  have  a  constitution  analogous  to  that  of  the  substances 
mentioned.  474.  Give  composition,  properties,  and  mode  of  manufacture  of, 


382  CONSIDERATION  OF  CARBON  COMPOUNDS. 


49.     BENZENE   DEEIVATIVES  CONTAINING   NITROGEN. 

Aniline,  Phenyl-amine,  C6H5NH2.  The  constitution  of  amines, 
to  which  class  aniline  belongs,  has  been  considered  in  Chapter  47. 
Aniline  is  found  in  coal-tar  and  in  bone-oil;  it  is  manufactured  on 
a  large  scale  by  the  action  of  nascent  hydrogen  upon  nitro-benzene, 
iron  and  hydrochloric  acid  being  generally  used  for  generating  the 
hydrogen. 

Experiment  59.  Dissolve  20  c.c.  of  nitre-benzene  (this  may  be  obtained 
according  to  the  directions  given  in  Experiment  57,  using  larger  quantities  of 
the  material)  in  alcoholic  ammonia  and  pass  through  this  solution  hydrogen 
sulphide  as  long  as  a  precipitate  of  sulphur  is  produced ;  the  reaction  takes 
place  thus : 

C6H5N02    +    3H2S    =    C6H5NH2    +    2H2O     +    88. 

Evaporate  on  a  water-bath  to  expel  ammonium  sulphide  and  alcohol ;  add  to 
the  residue  dilute  hydrochloric  acid,  which  dissolves  the  aniline,  but  leaves  any 
unchanged  nitro-benzene  undissolved.  Separate  the  nitro-benzene  from  the 
aniline  chloride  solution,  evaporate  this  to  dryness,  mix  with  some  lime,  in 
order  to  liberate  the  aniline,  which  may  be  obtained  by  distillation  from  a  dry 
flask. 

Pure  aniline  is  a  colorless,  slightly  alkaline  liquid,  having  a  pecu- 
liar, aromatic  odor,  a  bitter  taste,  and  strongly  poisonous  properties. 
It  boils  at  184.5°  C.  (364°  F.).  Like  all  true  amines,  it  combines 
with  acids  to  form  well-defined  salts. 

Aniline  dyes.  The  crude  benzene  used  in  the  manufacture  of  aniline 
dyes  is  generally  a  mixture  of  benzene,  C6H6,  and  toluene,  C7H8. 
This  mixture  is  first  converted  into  nitro-benzene,  C6H5NO2,  and 
nitro-toluene,  C7H7NO2,  and  then  into  aniline,  C6H5NH2,  and  tolu- 
idine,  C7H7NH2.  When  these  substances  are  treated  with  oxidizing 
agents,  such  as  arsenous  and  arsenic  oxides,  hypochlorites,  chromic 
or  nitric  acid,  etc.,  various  substances  are  obtained  which  are  either 

and  tests  for  carbolic  acid.  475.  What  substances  are  known  as  terpenes, 
where  are  they  found  in  nature,  and  how  are  they  related  to  camphors  ?  476. 
What  relation  exists  between  benzoic  acid  and  oil  of  bitter  almond?  477. 
What  is  the  source  of  amygdalin>  to  which  class  of  substances  does  it  belong, 
and  what  are  the  products  of  its  decomposition  under  the  influence  of  emulsine  ? 
478.  Explain  the  process  for  the  manufacture  of  salicylic  acid  from  phenol, 
and  state  its  properties.  479.  Give  composition  and  properties  of  naphtalin 
and  naphtol.  480.  Give  tests  for  tannin,  state  the  source  from  which  it  is 
derived,  and  for  what  it  is  used. 


BENZENE  DERIVATIVES  CONTAINING  NITROGEN.          383 

themselves  distinguished  by  beautiful  colors  or  may  be  converted 
into  numerous  derivatives  showing  all  the  various  shades  of  red,  blue, 
violet,  green,  etc. 

As  an  instance  of  the  formation  of  an  aniline  dye  may  be  men- 
tioned that  of  rosaniline,  which  takes  place  thus : 

C6H7N     +     2C7H9N    +     30        :    C20H19N3     +     3H2O. 
Aniline.  Toluidine.  Rosaniline. 

Experiment  60.  To  some  of  the  aniline  obtained  by  performing  Experiment 
59  add  a  little  solution  of  bleaching  powder :  a  beautiful  purple  color  is  ob- 
tained. Treat  another  portion  with  sulphuric  acid  to  which  an  aqueous  solu- 
tion of  potassium  dichromate  has  been  added :  a  blue  color  is  produced.  A 
third  quantity  treat  with  solution  of  cupric  sulphate  and  potassium  chlorate : 
a  dark  color  is  the  result. 

Diphenyl-amine,  (06H5)2NH,  is  obtained  by  the  destructive  distillation  of 
triphenyl-rosaniline  (aniline  blue)  as  a  grayish  crystalline  substance,  slightly 
soluble  in  water,  more  soluble  in  acids.  A  0.2  per  cent,  solution  in  diluted 
sulphuric  acid  (forming  diphenyl-sulphonic  acid)  is  colored  intensely  blue  by 
nitric  acid ;  also,  temporarily  by  nitrous  acid  and,  somewhat  less  intensely, 
by  hypochlorous,  bromic,  and  iodic  acids,  and  a  number  of  other  oxidizing 
agents. 

Meta-phenylene-diamine,  or  Diamido-benzol,  C6H4(NH2)2,  is  obtained  by 
the  reduction  of  meta-dinitrophenol  as  a  grayish  crystalline  powder.  It  has 
strongly  basic  properties,  is  somewhat  soluble  in  water,  readily  soluble  in  alco- 
hol or  ether.  It  is  a  valuable  reagent  for  nitrites,  as  it  forms  with  even  traces 
of  nitrous  acid  an  intense  yellow  color. 

Sulphanilic  acid,  Aniline-para-sulphonic  acid,  C4H6.NH.2.S03H.  Obtained 
by  heating  1  part  of  pure  aniline  oil  with  2  parts  of  fuming  sulphuric  acid, 
and  purifying  the  product  by  crystallization. 

C6H5.NH2    +    H2S04    =    C6H4.NH2.SO3H     +    H2O. 

It  is  a  colorless  crystalline  substance,  soluble  in  182  parts  of  cold  water. 
When  sulphanilic  acid  is  acted  upon  by  nitrous  acid,  it  is  converted  into  diazo- 
benzol-sulphonic  acid,  C6H5NNSO4H,  which  is  of  interest  because  it  is  used  as  a 
reagent  in  Ehrlich's  diazo-reaction  in  urinary  analysis. 

Acetanilid,  Antifebrine,  C8H9NO  or  C6H5.NH.C2H3O  (Phenyl- 
acetamide).  The  term  anilid  is  used  for  derivatives  of  aniline  obtained 
from  this  compound  by  replacement  of  the  ammonia  hydrogen  (or 
amido  hydrogen)  by  radicals,  and  according  to  the  introduction  of  an 
alcohol  radical  or  acid  radical  a  distinction  is  made  between  "  alcohol 
anilids"  and  "acid  anilids." 

If  the  radical  used  for  replacing  the  hydrogen  in  aniline  is  acetyl, 
C2H3O,  the  radical  of  acetic  acid,  the  resulting  compound  is  acetanilid,. 


384  CONSIDERATION  OF  CARBON  COMPOUNDS. 


the  constitution  of  which  is  represented  in  the  formula 

It  is  obtained  by  boiling  together  for  one  or  two  days  equal  weights 
of  pure  aniline  and  glacial  acetic  acid,  distilling  and  collecting  the  por- 
tion which  passes  over  at  a  temperature  of  about  295°  C.  (5,63°  F.). 
The  distillate  solidifies  on  cooling  and  may  be  purified  by  recry  stall  iza- 
tion  from  solution  in  water.  The  chemical  change  taking  place  is  this  : 

C6H6NH2  +  C2H402  ==  C6H5.NH.C2H30  +  H2O. 

Pure  acetanilid  forms  white,  odorless  crystals  of  a  silken  lustre  and 
a  greasy  feeling  to  the  touch.  It  fuses  at  113°  0.  (235°  F.)  and  boils 
at  295°  C.  (563°  F.)  ;  it  is  but  slightly  soluble  in  cold,  much  more 
soluble  in  hot  water,  readily  soluble  in  alcohol  and  ether  ;  the  solu- 
tions have  a  neutral  reaction  and  are  not  colored  by  either  concen- 
trated sulphuric  acid  or  by  ferric  chloride. 

Analytical  reactions: 

1.  When  0.1  gramme  acetanilid  is  boiled  with  1  c.c.  hydrochloric 
acid  and  to  this  solution  is  added  1  c.c.  each  of  saturated  solutions  of 
carbolic  acid  and  of  bleaching  powder,  a  turbid  red  liquid  is  obtained 
which  turns  dark-blue  when  supersaturated  with  ammonia  water. 
(Plate  VI.,  6.) 

2.  On  heating  0.1  gramme  of  acetanilid  with  a  few  c.c.  of  concen- 
trated solution  (1  in  4)  of  potassium  hydroxide,  the  odor  of  aniline 
becomes  noticeable  ;  on  now  adding  chloroform,  and  again  heating, 
the  disagreeable  odor  ,of  the  poisonous  phenyl-isonitril,  C6H5NC,  is 
evolved. 

3.  A  mixture  of  equal  parts  of  acetanilid  and  sodium  nitrite 
sprinkled  upon  concentrated  sulphuric  acid  produces  a  bright-red 
color. 

Phenyl-hydrazine,  C6H5.NH.NH2.  Hydrazine  compounds  are  substances 
derived  from  the  hypothetical  body  N2H4  (or  NH2—  NH2)  by  replacement  of 
hydrogen  atoms  by  alcohol  radicals.  They  possess  strong  basic  properties  and 
unite  directly  with  acids,  like  amines  or  amides.  Phenyl-hydrazine  is  of 
interest  because  it  is  used  in  the  manufacture  of  antipyrine,  and  also  because 
it  is  a  valuable  reagent  for  the  detection  of  aldehydes  and  sugars. 

It  is  obtained  by  treating  aniline  chloride  first  with  sodium  nitrite,  and  then 
with  nascent  hydrogen.  It  is  an  oily  liquid  forming  white  crystals  at  a  low 
temperature  ;  it  is  sparingly  soluble  in  water,  but  readily  in  hydrochloric  acid, 
with  which  it  combines  to  form  the  hydrochloride 

Antipyrine,  CUH12N2O  or  C£H6NO(CH3)2N2O  (Phenyl-dimethyl- 
pyrazolori).  When  phenyl-hydrazine  is  heated  with  diacetic  ether, 


BENZENE  DERIVATIVES  CONTAINING  NITROGEN.          385 


r<TT3  /n  TT  \r\  /O>  a  substance  is  formed  known  as  phenyl-methyl- 

^2±12  W^ftA^-^ 

pyrazolon,  C10H10N2O. 

In  this  compound  a  second  hydrogen  atom  may  be  replaced  by 
methyl,  when  phenyl-dimethyl-pyrazolon  is  formed,  which  is  the 
substance  to  which  the  name  antipyrine  has  been  given. 

Antipyrine  is  a  white,  crystalline,  odorless  powder,  having  a  slightly 
bitter  taste;  it  fuses  at  113°  C.  (235°  F.),  is  soluble  in  less  than  its 
own  weight  of  water,  in  one  part  of  alcohol,  in  one  part  of  chloro- 
form, but  only  in  50  parts  of  ether. 

Analytical  reactions  : 

1.  0.2  gramme  of  antipyrine  dissolve  in  2  c.c.  of  nitric  acid  with- 
out change  of  color.    On  heating  slightly  the  liquid  assumes  a  yellow, 
then  an  intense  red  color.     (Plate  VI.,  7.) 

2.  2  c.c.  of  a  5  per  cent,  solution  of  antipyrine  treated  with  a  few 
drops  of  potassium  nitrite  solution  yield  an  intense  green  color  on 
the  addition  often  drops  of  acetic  acid.     (Plate  VI.,  8.)     In  a  more 
concentrated  solution  green  crystals  of  nitroso-antipyrine  form  on 
standing. 

3.  The  addition  of  ferric  chloride  to  solution  of  antipyrine  causes 
a  deep  red  color. 

4.  Mercuric   chloride,  as  well  as  tannic  acid,  produces  a  white 
precipitate. 

Saccharine,  C7H5SO3N  or  C6H4.CO.SO2NH  (Benzole  sulphinide, 
Anhydro  ortho-sulphamine-benzoic  acid).  This  substance  is  a  deriva- 
tive of  benzoic  acid,  C6H5.CO2H,  obtained  from  it  by  introdu- 
cing the  two  bivalent  radicals  SO2  and  NH  with  elimination  of 
water.  The  constitution  is,  therefore,  represented  by  the  formula 


Practically,  saccharine  is  not  made  from  benzoic  acid,  but  from 
toluol,  C6H5.CH3,  by  a  series  of  rather  complicated  synthetical  pro- 

cesses. 

Saccharine  is  a  white,  amorphous  or  somewhat  crystalline  powder,  having  a 
very  slight  odor  of  oil  of  bitter  almond,  which  becomes  more  perceptible  on 
heating  the  substance.  It  is  but  sparingly  soluble  in  water,  requiring  about  400 
parts  for  solution  ;  this  solution  is  slightly  acid  and  has  an  extremely  sweet 
taste,  which  is  yet  perceptible  when  saccharine  "is  dissolved  in  70,000  parts  of 
water,  which  shows  tjiat  it  is  about  280  times  sweeter  than  cane-sugar,  a  solution 
of  which  in  250  parts  of  water  is  yet  perceptibly  sweet.  Saccharine  is  soluble 

25 


386  CONSIDERATION  OF  CARBON  COMPOUNDS. 

in  alcohol  and  ether,  and  it  is  this  latter  property  which  is  made  use  of  in  testing 
sugar  (or  other  substances  insoluble  in  ether)  for  saccharine.  The  substances 
are  treated  with  ether,  which  is  filtered  off  and  evaporated,  when  the  saccharine 
may  be  recognized  by  its  taste  in  the  remaining  residue. 

Pyrrole,  C4H5N.  During  the  destructive  distillation  of  certain 
nitrogenous  matters  (chiefly  bones),  a  liquid  known  as  bone-oil  is  ob- 
tained, which  contains  a  number  of  nitrogenous  basic  substances, 
among  which  pyridineand  pyrrole  are  found.  Pyrrole  has  but  weak 
basic  properties,  is  insoluble  in  water  and  has  an  odor  like  chloroform. 

A  solution  of  pyrrole  in  alcohol,  treated  with  iodine  in  the  presence 
of  oxidizing  agents,  such  as  ferric  chloride,  deposits  after  some  time 
crystals  of  tetra-iodo  pyrrole,  C4HI4N.  This  compound  is  used  under 
the  name  of  iodol.  It  is  a  pale-yellow,  crystalline  powder,  almost 
insoluble  in  water,  soluble  in  3  parts  of  alcohol,  1  part  of  ether,  and 
15  parts  of  fatty  oils;  it  is,  when  pure,  tasteless  and  odorless,  and 
contains  of  iodine  88.97  per  cent. 

Pyridine,  C5H5N.  This  substance  has  been  mentioned  above  as 
being  a  constituent  of  bone-oil.  Other  substances  have  been  isolated 
from  this  oil  and  have  been  found  to  form  a  homologous  series : 

Pyridine,  C5H5N  Lutidine,  C7H9  N 

Picoline,  C6H7N  Colliding  C8HUN 

Pyridine  is  of  special  interest,  because  it  has  been  found  that  several 
of  the  alkaloids,  such  as  quinine,  cinchonine,  etc.,  when  oxidized, 
yield  acids  containing  nitrogen,  which  bear  to  pyridine  the  same 
relation  that  benzoic  acid  bears  to  benzene,  or  that  acetic  acid  bears 
to  methane. 

Thus,  when  nicotine  is  treated  with  oxidizing  agents,  nicotinic  acid, 
C6H5NO2,  is  obtained,  which,  when  distilled  with  lime,  breaks  up 
into  pyridine  and  carbon  dioxide,  thus  : 

C6H5N02    :       C5H5N    +    C02. 

The  relation  of  nicotinic  acid  to  pyridine,  of  benzoic  acid  to  ben- 
zene, acetic  acid  to  methane,  may  be  shown  thus  : 

CH3.H  C6H5.H  C5H4N.H 

Methane.  Benzene.  Pyridine. 

CH3.C02H  C6H5.C02H  C6H4N.CO2H. 

Acetic  acid.  Benzoic  acid.  Nicotinic  acid. 

Pyridine  is  also  obtained  together  with  another  basic  substance, 
termed  quinoline,  C9H7N,  by  distilling  quinine  or  cinchonine  with 
potash.  These  observations,  showing  an  intimate  relationship  between 


ALKALOIDS.  38? 

alkaloids  and  the  pyridine  and  quinoline  bases,  have  led  to  numerous 
experiments  made  with  the  view  of  either  solving  the  problem  of 
making  alkaloids  synthetically,  or  of  obtaining  substances  which 
might  have  physiological  actions  similar  to  those  of  the  alkaloids. 
The  result  of  these  efforts  has  been  the  introduction  into  the  materia 
medica  of  quite  a  number  of  new  remedies. 

Pyridine  is  a  colorless  liquid,  having  a  sharp,  characteristic  odor, 
strongly  basic  properties,  and  a  boiling-point  of  116°  C.  (241°  F.). 

Quinoline,  C9H7N  ( Chinoline),  has  been  mentioned  above  as  a  product  of  the 
distillation  of  quinine  with  potash ;  it  may  also  be  obtained  by  the  action  of 
sulphuric  acid  upon  a  mixture  of  aniline,  nitro-benzene,  and  glycerin.  It  is, 
like  pyridine,  a  colorless  liquid,  but  its  aromatic  odor  is  less  pleasant  and  its 
basic  properties  are  less  marked  than  those  of  pyridine.  Boiling-point  237°  C. 
(458°  F.). 

Kairine,  C10H13.NO.HC1.  The  name  kairine  has  been  given  to  the  hydro- 
chloride  of  methyl-oxychinoline  hydride.  It  is  a  white,  crystalline,  odorless 
powder,  soluble  in  6  parts  of  water  or  in  20  parts  of  alcohol. 

Thalline,  C10HUNO  (Tetra-hydro-paramethyl-oxyquinoline).  Quinoline  serves 
in  the  manufacture  of  thalline,  a  white,  crystalline  substance,  which  has  an 
aromatic  odor,  fuses  at  40°  C.  (104°  F.)  and  is  soluble  in  water,  alcohol,  and 
ether.  The  most  characteristic  feature  of  the  substance  is  that  it  is  colored 
intensely  green  by  various  oxidizing  agents,  such  as  ferric  chloride  and  others. 
Some  of  the  salts  of  thalline,  chiefly  the  sulphate,  tartrate,  and  tannate,  have 
been  used  medicinally. 

50.  ALKALOIDS. 

General  Remarks.  The  basic  substances  found  in  plants  are 
grouped  together  under  the  name  of  alkaloids,  this  term  signifying 
alkali-like,  in  allusion  to  the  alkaline  or  basic  properties  of  these 
substances.  They  belong  either  to  the  amines  (compounds  contain- 
ing carbon,  hydrogen,  and  nitrogen  only),  or  to  the  amides  (com- 

QUESTIONS. — 481.  From  what,  and  by  what  process  is  aniline  obtained; 
what  is  its  composition  and  what  its  constitution  ?  482.  How  are  aniline  dyes 
manufactured  from  aniline  ?  483.  What  is  the  difference  between  an  amide 
and  an  anilid  ?  484.  What  is  the  composition  of  antifebrine,  and  how  is  it 
made?  485.  State  the  properties  and  some  reactions  characteristic  of  anti- 
pyrine.  486.  What  is  saccharine,  and  what  are  its  properties  ?  487.  Mention 
some  constituents  of  bone-oil.  488.  State  the  composition  of  iodol.  489. 
Explain  the  relation  existing  between  methane,  benzene,  pyridine,  and  the 
compounds  obtained  from  these  three  bodies  by  introducing  carboxyl.  490. 
Mention  two  processes  by  which,  and  two  sources  from  which  pyridine  may  be 
obtained. 


388  CONSIDERATION  OF  CARBON  COMPOUNDS. 

pounds  containing,  besides  the  three  elements  named,  also  oxygen), 
and  show  their  derivation  from  ammonia  to  a  more  or  less  marked 
degree,  as,  for  instance,  in  their  power  to  combine  with  acids  without 
elimination  of  water,  to  combine  with  platinic  chloride  to  form 
insoluble  double  compounds,  etc. 

The  compounds  formed  by  the  direct  combination  of  alkaloids 
with  acids  are,  in  the  case  of  oxygen  acids,  named  like  other  salts  of 
these  acids,  for  instance,  sulphates,  nitrates,  acetates,  etc.  In  the 
case  of  halogen  acids,  however,  a  different  method  has  been  adopted, 
because  it  would  be  incorrect  to  apply  the  terms  chlorides  and 
bromides  to  substances  formed  not  by  the  combination  of  chlorine  or 
bromine  with  other  substances,  nor  by  the  replacement  of  hydrogen 
in  the  respective  hydrogen  acids  of  these  elements,  but  by  direct 
combination  of  these  acids  with  the  alkaloids.  The  terms  hydro- 
chloride  and  hydrobromide  would  have  been  very  appropriate,  but  the 
terms  hydrochlorate  and  hydrobromaie  have  been  adopted  by  the 
U.  S.  P.  for  the  compounds  obtained  by  direct  union  of  alkaloids 
with  hydrochloric  and  hydrobromic  acids. 

Alkaloids  are  found  in  the  leaves,  stems,  roots,  barks,  and  seeds  of 
various  plants ;  it  often  happens  that  a  certain  alkaloid  is  found  in 
the  different  species  of  one  family,  and  it  is  also  often  the  case  that 
various  alkaloids  of  a  similar  composition  are  found  in  the  same 
plant. 

General  properties  of  alkaloids  : 

1.  They  combine  with  acids  (without  elimination  of  water)  to  form 
well-defined  salts,  and  are  set  free  from  the  solutions  of  these  salts 
by  alkalies  and  alkali  carbonates. 

2.  Those  containing  no  oxygen  (amines)  are,  in  most  cases,  volatile 
liquids,  those  containing  oxygen  (amides),  are  non-volatile  solids. 

3.  The  volatile  alkaloids  have  a  peculiar,  disagreeable  odor  remind- 
ing of  ammonia ;  the  non-volatile  alkaloids  are  odorless. 

4.  Most  solid  alkaloids  fuse  at  a  temperature  above  100°  C.  (212° 
F.)  without  decomposition,  but  are  decomposed  when  the  heat  is 
raised  much  beyond  the  fusing- point. 

5.  Most  alkaloids  are  insoluble,  or  nearly  so,  in  water,  but  soluble 
in  alcohol,  chloroform,  benzene,  acetic  ether,  and  many  also  in  ether. 

6.  The  chlorides,  sulphates,  nitrates,  acetates  (and  most  other  salts) 
of  alkaloids  are  either  soluble  in  water,  or  in  water  which  has  been 
slightly  acidulated,  and  also  in  alcohol ;  but  they  are  insoluble,  or 
nearly  so,  in  ether,  acetic  ether,  chloroform  (except  veratrine  and 


PLATE    VII. 


ALKALOIDS. 


Morphine  treated  with  nitric  acid. 


Morphine  treated  with   solution 
of  ferric  chloride. 


Codeine    treated    with    bromine 
water  and  ammonia  water. 


Quinine    treated    with    chlorine 
water  and  ammonia  water. 


Strychnine  treated  with  sulphuric 
acid  and  potassium  dichromate. 


Br ii cine  treated  with  nitric  acid 
and  with  sodium  thiosulphate. 


Physostigmine  treated  succes- 
sively with  ammonia  water,  alcohol, 
acetic  acid,  and  again  with  ammonia 
water. 


Veratrine  treated  with  sulphuric 
acid. 


ALKALOIDS:  389 

narcotine),  arnyl  alcohol  (except  veratrine  and  quinine),  benzene,  and 
benzin. 

7.  The  solid  alkaloids,  as  well  as  their  salts,  may  be  obtained  in 
a  crystalline  state. 

8.  Most  alkaloids  are  Avhite. 

9.  Most  alkaloids  have  a  very  strong,  generally  bitter  taste. 

10.  Most  alkaloids  act  very  energetically  upon  the  animal  system. 

11.  From  the  aqueous  solutions  of  alkaloid  salts,  the  solid  alkaloids 
are  precipitated  by  alkali  hydroxides,  in  an  excess  of  which  reagents 
some  alkaloids  (morphine,   for  instance)  are  soluble.     Alkali  car- 
bonates and  bicarbonates  liberate  all,  and  precipitate  most  alkaloids ; 
not  precipitated  by  bicarbonates  are  strychnine,  brucine,  veratrine, 
atropine,  and  a  few  rare  alkaloids. 

Most  alkaloids  give  precipitates  with  tannic  acid,  picric  acid, 
phospho-molybdic  acid,  potassium  mercuric  iodide ;  and  the  higher 
chlorides  of  platinum,  .gold,  and  mercury. 

12.  Most  alkaloids  give  beautiful  color  reactions  when  treated  with 
oxidizing  agents,  such  as  nitric  acid,  chloric  acid,  chromic  acid,  ferric 
chloride,  chlorine  water,  etc. 

A  decinormal  solution  of  mercuric-potassium  iodide,  HgI2.(KI)2,  made  by 
dissolving  13.546  grammes  mercuric  chloride  and  49.8  grammes  potassium 
iodide  in  1000  c.c  of  water,  is  known  as  Mayer's  solution.  This  precipitates  all 
alkaloids,  forming  with  them  white  or  yellowish-white,  generally  crystalline 
compounds  of  definite  composition,  for  which  reason  this  solution  is  used  for 
volumetric  determination  of  alkaloids.  (In  most  cases  the  alkaloid  replaces 
the  potassium  in  the  potassium-mercuric  iodide.) 

Phospho-molybdic  acid,  mentioned  above  as  a  reagent  for  alkaloids,  is  pre- 
pared as  follows :  15  grammes  ammonium  molybdate  are  dissolved  in  a  little 
ammonia  water  and  diluted  with  water  to  100  c.c.  This  solution  is  poured 
gradually  into  100  c.c.  of  nitric  acid,  specific  gravity  1.185,  and  to  this  mixture 
is  added  a  warm  6  per  cent,  solution  of  sodium  phosphate  as  long  as  a  precipi- 
tate is  produced.  This  precipitate  is  collected  on  a  filter,  washed  and  dissolved 
in  very  little  sodium  hydroxide  solution ;  the  solution  is  evaporated  to  dryness, 
further  heated  until  all  ammonia  has  been  expelled  and  the  residue  dissolved 
in  10  parts  of  water.  To  this  solution  is  added  a  quantity  of  nitric  acid  suffi- 
cient to  redissolve  the  precipitate  which  is  formed  at  first.  This  reagent  gives 
precipitates  not  only  with  the  alkaloids,  but  also  with  the  salts  of  potassium 
and  ammonium. 

General  mode  of  obtaining-  alkaloids.  The  disintegrated  veg- 
etable substance  (bark,  seeds,  etc.)  is  extracted  with  acidified  water, 
which  dissolves  the  alkaloids.  When  the  alkaloid  is  volatile,  it  is 
obtained  from  this  solution  by  distillation,  after  having  been  liberated 
by  an  alkali. 


390  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Non  volatile  alkaloids  are  precipitated  from  the  acid  solution  by 
the  addition  of  an  alkali,  and  the  impure  alkaloid  thus  obtained  is 
purified  by  again  dissolving  in  an  acid  and  reprecipitating,  or  by  dis- 
solving in  alcohol  and  evaporating  the  solution. 

As  the  quantity  of  alkaloids  in  plants,  and  consequently  in  the  aqueous 
extract  made  from  them,  is  often  so  small  that  the  precipitation  process  gives 
unsatisfactory  results,  a  second  method  known  as  the  shaking-out  process  is  often 
employed  for  the  separation  of  alkaloids.  In  using  this  process  the  con- 
centrated aqueous  extract,  to  which  a  suitable  alkaline  precipitant  has  been 
added,  is  agitated  with  a  liquid  (such  as  chloroform)  not  miscible  with  water 
and  acting  as  a  solvent  upon  the  alkaloids.  The  operation  is  performed  in  an 
apparatus  known  as  separator  or  separatory  funnel,  consisting  of  a  globular  or 
cylindrical  glass  vessel,  provided  with  a  well-fitting  stopper  and  an  outlet-tube 
containing  a  glass  stopcock.  Having  introduced  into  this  vessel  the  extract 
and  solvent,  the  latter  is  made  to  dissolve  the  alkaloids  present  by  a  rapid 
rotation  of  the  separator.  As  the  aqueous  solution  and  the  solvent  do  not  mix, 
but  form  two  distinct  layers  one  above  the  other,  they  may  be  conveniently 
separated  by  opening  the  stopcock  until  the  heavier  liquid  has  run  out.  By 
evaporation  of  the  liquid,  used  as  a  solvent,  the  alkaloids  may  be  obtained  in  a 
more  or  less  pure  condition. 

Antidotes.  In  cases  of  poisoning  by  alkaloids  the  stomach-pump  and  emetics 
(zinc  sulphate)  should  be  applied  as  soon  as  possible ;  astringent  liquids  may  be 
given,  because  tannic  acid  forms  insoluble  compounds  with  most  of  the  alkaloids. 
In  some  cases  special  physiological  antidotes  are  known,  and  should  be  used. 

Detection  of  alkaloids  in  cases  of  poisoning*.  The  separation 
and  detection  of  poisonous  alkaloids  in  organic  matter  (food,  contents 
of  stomach,  etc.),  especially  when  present  in  very  small  quantities,  as 
is  generally  the  case,  is  one  of  the  most  difficult  tasks  of  the  toxi- 
cologist,  and  none  but  an  expert  who  has  made  himself  thoroughly 
familiar  with  the  methods  of  discovering  minute  quantities  of  organic 
poisons  in  the  animal  system  should  undertake  to  make  such  an 
analysis  in  case  legal  proceedings  depend  on  the  result  of  the 
chemist's  report. 

Of  the  various  methods  applied  for  the  separation  of  alkaloids  from  organic 
matter,  the  following  may  be  mentioned : 

The  substance  to  be  examined  is  properly  comminuted  (if  this  be  necessary) 
and  repeatedly  digested  at  40°  to  50°  C.  (104°  to  122°  F.)  with  water  slightly 
acidulated  with  sulphuric  acid.  The  filtered  liquids  (containing  the  sulphates 
of  the  alkaloids)  are  evaporated  over  a  water-bath  to  a  thin  syrup,  which  is 
mixed  with  three  or  four  times  its  own  volume  of  alcohol ;  this  mixture  is 
digested  at  about  35°  C.  (95°  F.)  for  several  hours,  cooled,  filtered,  and  again 
evaporated  nearly  to  dryness.  (By  this  treatment  with  alcohol  many  substances 
soluble  in  the  acidified  water,  but  insoluble  in  diluted  alcohol,  are  eliminated 
and  left  on  the  filter,  whilst  the  alkaloids  remain  in  solution  as  sulphates.) 


ALKALOIDS. 


391 


A  little  water  is  now  added  to  the  residue,  and  this  solution,  which  should  yet 
have  a  slight  acid  reaction,  is  shaken  with  about  three  times  its  own  volume  of 
acetic  ether,  which  dissolves  some  coloring  and  extractive  matters,  but  does  not 
act  upon  the  alkaloid  salts.  The  two  strata  of  liquids  which  form  on  standing 
in  a  tube  are  separated  by  means  of  a  pipette,  and  the  operation  is  repeated,  if 
necessary,  i.  e.,  if  the  ether  should  have  been  strongly  colored. 

The  remaining  acid  aqueous  solution  is  next  slightly  supersaturated  with 
sodium  carbonate,  which  liberates  the  alkaloids.  Upon  now  shaking  the  solu- 
tion with  acetic  ether,  all  alkaloids  are  dissolved  in  this  liquid,  which,  after 
being  separated  from  the  aqueous  solution,  leaves  upon  evaporation,  at  a  low 
temperature,  the  alkaloids  generally  in  a  sufficiently  pure  state  for  recognition 
by  special  tests.  It  may,  however,  be  necessary  to  purify  the  residue  further 
by  neutralizing  with  an  acid,  allowing  to  crystallize  in  a  watch-glass,  and  sep- 
arating the  small  crystals  from  adhering  mother-liquor. 

The  above  method  for  detecting  alkaloids  in  the  presence  of  organic  matter 
generally  answers  the  requirements  of  students. 

The  practical  toxicologist  has  in  most  cases  of  poisoning  some  data  (deduced 
from  the  symptoms  before  death,  or  from  the  results  of  the  post-mortem  exam- 
ination) pointing  to  a  certain  poison,  which,  of  course,  facilitate  his  work  con- 
siderably. 

Important  alkaloids. 

a.  Liquid  and  volatile  alkaloids. 

Sparteine,  C15H26N2  Scoparius. 

Coniine,  C8  H17N  Conium  maculatum. 

Nicotine,  C10HUN2  Tobacco  plant. 

b.  Solid  and  fixed  alkaloids. 


Morphine, 

C17H19N03 

10.00  per  cent. 

Codeine, 

C18H21N03 

0.25 

Thebaine, 

C19H21N03 

0.15        " 

Papaverine, 

C21H21N04 

1.00        " 

Narcotine, 

C22H23N07 

1.30 

Narceine, 
Pseudo-morphine, 
Protopine, 
Codamine, 

C23H29N09 
C17H19N04  - 
C20H19N05 
C20H23N04 

0.70        " 

In  opium. 
The  percentages  given 
are  an   average,  but 
vary  widely. 

Laudamine, 

C21H27N04 

less  than  0.1 

Meconidine, 

C21H23N04 

per  cent. 

Cryptopine, 

C21H23N05 

• 

Laudanosine, 

C21H27N04  J 

Quinine, 

C20H24N202 

-f  3H20      ] 

Cinchonine, 
Quinidine, 

C19H22N20 
isomere  to  quinine          [  In  cinchona  bark. 

Cinchonidine, 

isomere  to  cinchonine  | 

Strychnine, 

C21H22N202 

1 

Brucine, 

C23H26N204  +  (4H2O)  /  In  nux  vomica. 

Atropine, 

C17H23N03 

Hyoscyamine, 

C17H23N03 

In  solanacese. 

Hyoscine, 

C17H21N04 

392  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Cocaine,  CnH21NO4  Erythroxylon  coca. 

Veratrine,  ?  Asagrsea  officinalis. 

Aconitine,  C33H45NO12  Aconitum  napellus. 

Colchicine,  C22H25NO6  Colchicum  autumnale. 

Berberine,  C20H17NO4  Berberis  vulgaris. 

Hydrastine,  C21H21NO6  j  Hydrastis  canadensis. 

Hydrastinine,  CnHnNOg 

Physostigmine,  C15H21N3O2  Calabar  bean. 

Pilocarpine,  CUH16N2O2  Pilocarpus. 

Caffeine,  C8  H10N  4O2  +  H2O  Coffee,  tea. 

Theobromine,  C7  H8  N4O2  Seeds  of  theobroma  cacao. 

Sparteine,  C15H26N2.  This  alkaloid,  found  in  scoparius  (broom, 
Irish  broom),  is  a  colorless,  oily  liquid,  turning  brown  on  exposure 
to  air  and  light.  It  has  a  slight  aniline-like  odor. 

Sparteine  sulphate,  C15H26N2H2S04  +  411,0,  is  obtained  by  saturating  the 
alkaloid  with  sulphuric  acid ;  it  is  a  colorless,  crystalline  salt,  readily  soluble 
in  water.  An  ethereal  solution  of  the  salt,  to  which  a  few  drops  of  ammonia 
water  have  been  added,  deposits  on  the  addition  of  an  ethereal  solution  of 
iodine,  minute  dark  greenish-brown  crystals. 

Coniine,  C8H17N,  occurs  in  conium  maculatum  (hemlock),  accom- 
panied by  two  other  alkaloids.  It  is  a  colorless,  oily  liquid,  having 
a  disagreeable,  penetrating  odor. 

Nicotine,  C10H14N2.  Tobacco  leaves  contain  from  2  to  8  per  cent, 
of  nicotine,  which  is  a  colorless,  oily  liquid,  having  a  caustic  taste 
and  a  disagreeable,  penetrating  odor.  It  gives  with  hydrochloric 
acid  a  violet,  with  nitric  acid  an  orange  color. 

Opium  is  the  concrete,  milky  exudation  obtained,  in  the  Orient, 
by  incising  the  unripe  capsules  of  papaver  somniferum,  poppy. 
Chemically,  opium  is  a  mixture  of  a  large  number  of  substances, 
containing  besides  glucose,  fat,  gum,  albumin,  wax,  volatile  and 
coloring  matter,  meconic  acid,  etc.,  not  less  than  sixteen  or  eighteen 
different  alkaloids,  many  of  which  are,  however,  present  in  minute 
quantities. 

Ordinary  opium  should  contain  not  less  than  9  per  cent.,  and  when 
dried  at  85°  C.  (185°  F.)  from  13  to  15  per  cent,  of  morphine. 

Dried  and  powdered  opium,  after  having  been  exhausted  with 
about  ten  times  its  weight  of  stronger  ether  (which  dissolves  chiefly 
the  narcotine,  but  not  the  morphine  salts),  the  ethereal  solution 
filtered  off,  and  the  weight  of  the  opium  restored  by  sugar  of  milk, 
forms  the  deodorized  opium  of  the  U.  S.  P. 


ALKALOIDS.  393 

Experiment  61.  Determine  quantitatively  the  amount  of  morphine  in  a 
sample  of  opium  by  using  the  U.  S.  P.  method,  which  is  as  follows :  Introduce 
10  grammes  of  opium  (which,  if  fresh,  should  be  in  very  small  pieces,  and  if 
dry,  in  very  fine  powder)  into  a  bottle  having  a  capacity  of  about  300  c.c.,  add 
100  c.c.  of  water,  cork  it  well,  and  agitate  it  frequently  during  twelve  hours. 
Then  pour  the  whole  as  evenly  as  possible  upon  a  wetted  filter  having  a  diam- 
eter of  12  centimeters,  and,  when  the  liquid  has  drained  off,  wash  the  residue 
with  water  until  150  c.c.  of  filtrate  are  obtained.  Then  transfer  the  moist 
opium  back  to  the  bottle,  add  50  c.c.  of  water,  agitate  repeatedly  during  fifteen 
minutes,  and  return  the  whole  to  the  filter.  Wash  the  residue  with  water  until 
the  filtrate,  to  be  collected  in  a  second  flask,  measures  150  c.c. :  finally,  collect 
20  c.c.  more  of  a  third  filtrate.  Next  evaporate  in  a  tared  capsule,  first,  the 
second  filtrate  to  a  small  volume,  then  add  the  first  filtrate,  rinsing  the  vessel 
with  the  third  filtrate,  and  continue  the  evaporation  until  the  residue  weighs 
14  grammes.  Transfer  this  residue  to  a  tared  100  c.c.  flask  and  rinse  the  cap- 
sule with  a  few  drops  of  water  at  a  time,  until  the  entire  solution  weighs  20 
grammes.  Then  add  12.2  c.c.  of  alcohol,  shake  well,  add  25  c.c.  of  ether,  and 
shake  again.  Now  add  3.5  c.c.  of  ammonia  water  from  a  pipette,  stopper  the 
flask,  shake  it  thoroughly  during  ten  minutes,  and  then  set  it  aside  for  at  least 
six  hours. 

Place  in  a  funnel  two  rapidly-acting  filters,  of  a  diameter  of  7  centimeters, 
one  within  the  other,  wet  them  with  ether,  and  decant  the  ethereal  solution 
upon  the  filter.  Add  10  c.c.  of  ether  to  the  contents  of  the  flask,  rotate  it,  and 
again  decant  the  ethereal  layer  upon  the  filter.  Repeat  this  operation  with 
another  portion  of  10  c.c.  of  ether.  Then  pour  into  the  filter  the  contents  of 
the  flask  in  such  a  way  as  to  transfer  the  greater  portion  of  the  crystals  to  the 
filter,  accomplishing  this  finally  by  washing  the  flask  with  several  portions  of 
water,  using  not  more  than  10  c.c.  in  all.  Allow  the  filter  to  drain,  then  apply 
water  to  the  crystals,  drop  by  drop,  until  they  are  practically  free  from  mother- 
water,  and  afterward  wash  them,  drop  by  drop,  from  a  pipette,  with  alcohol 
previously  saturated  with  powdered  morphine.  When  this  has  passed  through, 
displace  the  remaining  alcohol  by  ether,  using  about  10  c.c.  Allow  the  filter  to 
dry  at  a  temperature  not  exceeding  60°  C.  (140°  F.)  until  its  weight  remains 
constant,  then  transfer  the  crystals  to  a  tared  watch-glass  and  weigh  them. 
The  weight  found,  multiplied  by  10,  represents  the  percentage  of  crystallized 
morphine  obtained  from  the  specimen  examined. 

The  explanation  of  the  above  process  is  as  follows :  By  extracting  opium 
with  water  a  liquid  is  obtained  containing  in  solution  the  total  quantity  of 
opium  alkaloids,  in  the  form  of  salts,  alongside  of  numerous  other  substances. 
As  it  is  desirable  to  work  analytically  with  small  volumes  of  liquids  (in  order 
to  avoid  loss  through  solubility  of  the  precipitate),  the  aqueous  solutions  are 
evaporated  to  a  small  bulk.  The  addition  of  ammonia  water  causes  the  decom- 
position of  the  alkaloidal  salts  with  precipitation  of  morphine,  while  certain 
other  alkaloids,  especially  narcotine,  remain  dissolved  in  the  ether  which  for 
this  purpose  has  been  added  previously. 

Morphine,  Morphina,  C17H19NO3.H2O  =  303  (Morphia).  A 
white  crystalline  powder,  or  colorless,  shining,  prismatic  crystals, 
odorless,  of  a  bitter  taste,  and  an  alkaline  reaction  to  litmus ;  almost 


394  CONSIDERATION  OF  CARBON  COMPOUNDS. 

insoluble  in  ether  and  chloroform,  very  slightly  soluble  in  cold 
water,  soluble  in  300  parts  of  cold  and  36  parts  of  boiling  alcohol ; 
heated  for  some  time  at  100°  C.  (212°  F.)  it  becomes  anhydrous  ;  at 
254°  C.  (489°  F.)  it  melts,  forming  a  black  liquid  ;  heated  with 
excess  of  hydrochloric  acid  for  some  hours,  under  pressure,  to  150°  C. 
(302°  F.),  it  loses  water,  and  is  converted  into  apomorphine,  C17H17 
NO2,  a  crystalline,  solid  alkaloid,  valuable  as  an  emetic.  Apomor- 
phine hydrochlorate,  C17H17NO2.HC1,  is  official;  it  is  a  white  salt, 
which  turns  green  when  exposed  to  the  air,  especially  in  the  presence 
of  moisture. 

The  above-mentioned  process  for  the  quantitative  estimation  of 
morphine  in  opium  may  be  used  for  its  manufacture;  the  crude 
morphine  thus  obtained  is  purified  by  crystallization. 

Morphine  combines  with  acids,  and  of  the  salts  are  official : 

Morphine  acetate,  Morphinse  acetas,  C17H19NO3.C2H4O2.3H2O. 

Morphine  hydrochlorate,  Morphinae  hydrochloras,  C17H19NO3.HC1.3H2O. 
Morphine  sulphate,  Morphinse  sulphas,  (C17H19NO3)2H2SO4.5H2O. 

The  above  three  salts  are  white,  and  soluble  in  water. 

Analytical  reactions : 

1.  Morphine  or  a  morphine  salt  sprinkled  upon  nitric  acid  assumes 
an  orange-red  color,  and  then  produces  a  reddish  solution,  gradually 
changing  to  yellow.     (Plate  VII.,  1 .) 

2.  Neutral  solution  of  ferric  chloride  causes  a  blue  color  with 
morphine  or  with  neutral  solutions  of  morphine  salts ;  the  color  is 
changed  to  green  by  an  excess  of  the  reagent,  and  is  destroyed  by 
free  acids  or  alcohol,  but  not  by  alkalies.     (Plate  VII.,  2.) 

3.  A  fragment  of  iodic  acid  added  to  a  strong  solution  of  a  mor- 
phine salt  is  decomposed,  with  liberation  of  iodine,  which  imparts  a 
violet  color  to  chloroform  upon  shaking  the  latter  with  the  mixture. 

4.  A  mixture  of  2  parts  of  morphine  and  1  part  of  cane-sugar 
added  to  concentrated  sulphuric  acid  gives  a  rose-red  color. 

5.  Morphine  dissolves  in  cold,  concentrated  sulphuric  acid,  forming 
a  colorless  solution,  which,  after  standing  for  several  hours,  turns 
pink  or  red  on  the  addition  of  a  trace  of  nitric  acid. 

6.  Aqueous  or  acid  solutions  of  morphine  salts  are  precipitated  by 
alkaline  hydroxides ;  the  precipitated  morphine  is  soluble  in  potas- 
sium or  sodium  hydroxide,  but  not  in  ammonium  hydroxide. 

7.  Neutral  solutions  of  morphine  afford  yellow  precipitates  with 
the  chloride  of  gold  or  platinum,  with  potassium  chromate  or  dichro- 
mate,  and  with  picric  acid,  but  not  with  mercuric  chloride. 


ALKALOIDS.  395 

Codeine,  Codeina,  C18H21NO3.H2O  =  317.  A  white,  crystalline 
powder,  sparingly  soluble  in  cold  water,  easily  soluble  in  alcohol  and 
chloroform.  It  is  neutral  to  litmus,  and  has  a  faintly  bitter  taste. 

Analytical  reactions: 

1.  On  adding  to  5  c.c.  of  an  aqueous  solution  of  codeine  (1  in  100) 
10  drops  of  bromine  water,  shaking  so  as  to  redissolve  the  precipitate 
formed,  and  adding  after  a  few  minutes  some  ammonia  water,  the 
liquid  assumes  a  claret-red  tint.     (Plate  VII.,  3.) 

2.  Codeine,  dissolved  in  sulphuric  acid  containing  1  per  cent,  of 
sodium  molybdate,  forms  at  first  a  dirty-green  solution,  which  after 
a  while  becomes  pure  blue,  and  gradually  fades  within  a  few  hours 
to  pale  yellow. 

3.  Codeine,  dissolved  in  sulphuric  acid,  forms  a  colorless  liquid, 
which,  upon  being  warmed  with  a  trace  of  ferric  chloride,  becomes 
deep  blue. 

4.  Crystals  of  codeine  sprinkled  upon  nitric  acid  assume  a  red 
color,  but  the  acid  will  acquire  only  a  yellow,  not  a  red  color.     (Dif- 
ference from  morphine.) 

Narcotine,  C,2H.23N07,  and  Narceine,  C23H29N09.2H20,  are  white,  crystalline 
opium  alkaloids,  which  are  almost  insoluble  in  water,  soluble  in  alcohol. 
Concentrated  sulphuric  acid  forms  with  narcotine  a  solution  which  is  at  first 
colorless,  but  turns  yellow  in  a  few  minutes,  and  purple  on  heating.  Narceine 
dissolves  in  concentrated  sulphuric  acid  with  a  gray-brown  color,  which  changes 
to  red  when  heated. 

Meconic  acid,  C7H4O7.3H2O.  A  tribasic  acid,  characteristic  of 
opium,  in  which  it  exists  to  the  extent  of  3  or  4  per  cent.,  most 
likely  combined  with  the  alkaloids.  It  is  a  white,  crystalline  sub- 
stance, soluble  in  water  and  alcohol. 

Meconic  acid  forms  with  ferric  chloride  a  blood-red  color,  which  is 
not  affected  by  dilute  acids  or  by  mercuric  chloride  (different  from 
ferric  sulphocyanate),  but  disappears  on  the  addition  of  stannous 
chloride  and  of  the  alkali  hypochlorites.  This  test  may  be  used  in 
cases  of  poisoning  to  decide  whether  opium  or  morphine  is  present. 

Cinchona  alkaloids.  The  bark  of  various  species  of  cinchona 
contains  a  number  of  alkaloids,  of  which  the  most  important  are 
quinine,  cinchonine,  quinidine,  and  cinchonidine.  These  alkaloids 
exist  in  the  bark  in  combination  with  a  peculiar  acid,  termed  Jcinic 
add.  The  quantity  and  relative  proportion  of  the  alkaloids  vary 
widely  in  different  barks,  but  the  official  bark  should  contain  not  less 
than  5  per  cent,  of  total  alkaloids,  and  at  least  2.5  per  cent,  of  quinine. 


396  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Determination  of  the  total  alkaloids  and  of  quinine  in  Cinchona.  The 
U.  S.  P.  has  adopted  the  following  method  for  the  assay  of  cinchona : 

1.  For  total  alkaloids.    To  20  grammes  of  finely-powdered   cinchona,  and 
contained  in  a  glass-stoppered  flask,  add  200  c.c.  of  a  previously  prepared  mix- 
ture of  19  volumes  of  alcohol,  5  volumes  of  chloroform,  and  1  volume  of 
ammonia  water ;  shake  the  mixture  frequently  during  four  hours.     Then  filter 
into  a  bottle  through  a  funnel  containing  a  pellet  of  cotton,  in  such  a  manner 
that  no  material  loss  by  evaporation  may  result.     Transfer  100  c.c.  of  the 
filtrate  to  a  beaker  and  evaporate  to  dryness.     Dissolve  the  residue  of  crude 
alkaloids  thus  obtained  in  10  c.c.  of  water  and  4  c.c.  of  normal  sulphuric  acid  ; 
with  the  aid  of  a  gentle  heat,  filter  the  cooled  solution  into  a  separatory  funnel, 
and  wash  the  beaker  and  filter  until  the  filtrate  no  longer  has  an  acid  reaction, 
using  as  small  a  quantity  of  water  as  possible.     Now  add  5  c.c.  of  normal 
potassium  hydrate,  or  such  an  amount  as  will  render  the  liquid  decidedly 
alkaline,  and  extract  the  alkaloids  by  shaking  the  mixture,  first  with  20  c.c., 
and  then  repeatedly  with  10  c.c.  of  chloroform,  until  a  drop  of  the  last  chloro- 
form extraction,  when  evaporated  on  a  watch-glass,  no  longer  leaves  a  residue. 
Evaporate  the  chloroformic   extracts  in  a  tared  beaker,  dry  the  residue  at 
100°  C.  (212°  F.),  and  weigh.     The  weight  found,  multiplied  by  10,  will  give 
the  percentage  of  total  alkaloids. 

2.  For  quinine.    Transfer  50  c.c.  of  the  clear  filtrate  remaining  over  from  the 
preceding  process  to  a  beaker,  evaporate  it  to  dryness,  and  proceed  as  directed 
in  the  assay  for  total  alkaloids,  using,  however,  only  one-half  the  amounts  of 
volumetric  acid  and  alkali  there   directed      Add  the  united   chloroformic 
extracts  gradually,  and  in  small  portions  at  a  time,  to  about  5  grammes  of 
powdered  glass  contained  in  a  porcelain  capsule  placed  over  a  water-bath. 
After  the  chloroform  has  been  expelled  moisten  the  residue  with  ether,  and, 
having  placed  a  funnel  containing  a  filter  of  a  diameter  of  7  centimeters,  and 
well  wetted  with  ether,  over  a  small  graduated  tube  (A),  transfer  to  the  filter 
the  ether-moistened  residue  from  the  capsule.     Rinse  the  latter  several  times 
with  fresh  ether,  so  as  to  transfer  the  whole  of  the  residue  to  the  filter,  then 
percolate  with  ether,  drop  by  drop,  until  10  c.c.  of  percolate  have  been  obtained. 
Then  collect  another  percolate  of  10  c.c.  by  similar  slow  percolation  with  ether, 
in  a  second  graduated  tube  (B).     Transfer  the  contents  of  the  two  tubes  com- 
pletely (using  ether  for  washing)  to  two  small,  tared  capsules  (marked  A  and 
B),  evaporate  at  100°  C.  (212°  F.)  and  weigh  them.     From  the  weight  of  residue 
obtained  in  A  deduct  that  contained  in  B,  and  multiply  the  remainder  by 
twenty.    The  product  represents,  approximately,  the  percentage  of  quinine, 
containing  one  molecule  of  water. 

The  explanation  of  the  above  processes  is  this :  By  the  action  of  ammonia 
water  the  cinchona  alkaloids  are  set  free  and  become  dissolved  in  the  alcoholic 
chloroform  used  for  extraction  of  the  bark.  The  liquid  also  acts,  however,  as 
a  solvent  upon  other  substances,  for  which  reason  the  impure  alkaloids  are 
purified  by  dissolving  the  mass  in  acidified  water,  liberating  the  alkaloids  by 
caustic  potash  and  extracting  them  by  means  of  chloroform. 

While  the  direct  evaporation  of  this  chloroform  solution  gives  the  weight  of 
the  total  alkaloids,  a  separation  of  quinine  from  the  other  cinchona  alkaloids 
is  accomplished  by  ether,  in  which  quinine  is  much  more  soluble  than  the  rest 
of  the  alkaloids.  In  order  to  accomplish  the  extraction  with  ether  successfully 


ALKALOIDS.  397 

the  chloroformic  solution  is  made  to  evaporate  over  glass  powder,  by  which 
process  the  intimate  adhering  of  the  alkaloidal  particles  is  prevented.  The 
residue  in  capsule  A  contains  practically  all  the  quinine,  together  with  a 
portion  of  the  alkaloids  less  soluble  in  ether ;  the  residue  in  B  consists  almost 
entirely  of  these  alkaloids,  and  as  about  an  equal  quantity  of  them  is  contained 
in  A  and  B,  the  weight  of  B  is  deducted  from  that  of  A. 

Quinine,  Quinina,  C20H24N2O2.3H2O  =  378.  This  formula  rep- 
resents the  official  alkaloid,  but  it  is  also  known  anhydrous,  and  in 
combination  with  either  one  or  two  molecules  of  water.  The  anhy- 
drous quinine  is  a  resinous  substance,  whilst  the  crystallized  quinine 
is  a  white,  flaky,  amorphous  or  crystalline  powder,  having  a  very 
bitter  taste  and  an  alkaline  reaction.  It  is  nearly  insoluble  in  water, 
but  soluble  in  alcohol,  ether,  ammonia  water,  chloroform,  and  dilute 
acids.  When  heated  to  about  57°  C.  (134°  F.)  it  melts  ;  at  100°  C. 
(212°  F.)  it  loses  2  molecules  of  water,  the  remainder  being  expelled 
at  125°  C.  (257°  F.). 

Quinine  sulphate,  Quininae  sulphas,  (C20H24N2O2)2H2SO4.7H2O 
=  872.  This  salt,  containing  two  molecules  of  the  alkaloid  in 
combination  with  one  of  sulphuric  acid  and  seven  of  water,  is  the 
common  form  of  sulphate  of  quinine.  It  forms  snow-white,  silky, 
light  and  fine,  needle-shaped  crystals,  fragile  and  somewhat  flexible, 
making  a  very  light  and  easily  compressible  mass ;  it  has  a  very 
bitter  taste  and  a  neutral  reaction ;  it  is  soluble  in  740  parts  of  cold 
and  in  30  parts  of  boiling  water,  soluble  in  65  parts  of  alcohol,  but 
nearly  insoluble  in  ether  and  chloroform ;  it  readily  dissolves  in 
diluted  sulphuric  or  hydrochloric  acid. 

Quinine  bisulphate,  Quininse  bisulphas,  C20H24N2O2.H2SO4. 
7H2O  =  548.  This  salt  is  formed  when  the  common  sulphate  is 
dissolved  in  an  excess  of  diluted  sulphuric  acid.  It  crystallizes  in 
colorless,  silky  needles,  has  a  strongly  acid  reaction,  and  is  soluble 
in  10  parts  of  water. 

Quinine  hydrochlorate,  C20H24N2O2.HC1  2H2O  =  396.4 
Quinine  hydrobromate,  C20H24N2O2.HBr.2H2O  =  440.8 
Quinine  valerianate,  C20H24N2O2.C5H10O2.H2O  =  444. 

The  above  three  salts  are  obtained  by  dissolving  quinine  in  the 
respective  acids ;  they  are  white,  crystalline  substances  ;  the  first  two 
are  easily,  the  valerianate  is  sparingly  soluble  in  water. 

Iron  and  quinine  citrate  is  a  scale  compound  obtained  by  dissolving 
ferric  hydroxide  and  quinine  in  citric  acid,  evaporating,  etc. 


398  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Analytical  reactions : 

1.  Quinine  or  its  salts,  dissolved  in  water  or  in  dilute  acids,  give, 
after  having  been  shaken   with   fresh  chlorine  water,  or  bromine 
water,  an  emerald-green  color  on  the  addition  of  ammonium  hydrox- 
ide.    (Plate  VII.,  4.) 

The  reaction  is  readily  shown  by  treating  10  c.c.  of  a  solution 
(about  1  in  1500)  with  2  drops  of  bromine  water,  and  then  with  an 
excess  of  ammonia  water.  The  green  color  is  due  to  the  formation 
of  thalleioquin. 

2.  Solutions  of  quinine,  treated  with  chlorine  water,  then  with 
fragments  of  potassium   ferrocyanide,  turn  pink,  then  red  on  the 
addition  of  ammonium  hydroxide  not  in  excess. 

3.  Solutions  of  quinine  give  with  water  of  ammonia  a  white  pre- 
cipitate  of  quinine,  which   is    readily  dissolved   in   an   excess   of 
ammonia.     The  precipitate  is  also  soluble  in  about  twenty  times  its 
own  weight  of  ether  (the  other  cinchona  alkaloids  requiring  larger 
proportions  of  ether  for  solution). 

4.  Most  solutions  of  quinine,  especially  when  acidulated  with  sul- 
phuric acid,  show  a  vivid  blue  fluorescence. 

5.  Neutral  solutions  of  quinine 'are  precipitated  by  alkaline  oxa- 
lates. 

6.  Quinine  and  its  salts  form  colorless  solutions  with  concentrated 
sulphuric  acid.     A  dark  or  red  color  indicates  the  presence  of  other 
organic  substances. 

Quinidine,  C20H24N2O2.  Isomeric  with  quinine ;  it  gives,  like  the 
latter,  a  green  color  with  chlorine  water  and  ammonia,  and  forms 
fluorescent  solutions.  Unlike  quinine,  it  is  precipitated  from  neutral 
solutions  by  potassium  iodide.  The  sulphate  is  official. 

Cinchonine,  Cinchonina,  C19H22N2O  =  3O8.  This  alkaloid  is 
found  in  cinchona  bark  in  quantities  varying  from  0.5  to  3  per  cent. 
It  crystallizes  without  water,  forming  white  needles ;  it  is  almost 
insoluble  in  water,  soluble  in  116  parts  of  alcohol  or  in  163  parts  of 
chloroform,  readily  soluble  in  dilute  acids. 

By  dissolving  the  alkaloid  in  sulphuric  acid  is  obtained : 
Cinchonine  sulphate,  Cinchoni nee  sulphas,  (C19H221S"2O)2H2SO4.2H2O. 
It  is  a  white,  crystalline  substance.  Cinchonine  differs  from  quinine 
by  its  greater  insolubility  in  ether,  by  its  insolubility  in  ammonia 
water,  by  not  forming  fluorescent  solutions,  and  by  not  giving  a 
green  color  with  chlorine  water  and  ammonia. 


ALKALOIDS.        .  399 

Analytical  reactions: 

1.  Chlorine  water  added  to  the  solution  of  a  cinchonine  salt  pro- 
duces a  yellowish-white  precipitate  insoluble  in  excess  of  ammonia. 

2.  Potassium  ferrocyanide  solution  added  to  a  neutral  solution  of 
cinchonine  produces  a  white  precipitate  soluble  in  excess  of  the  re- 
agent.     Upon   adding   an   acid   to   this   solution   a   golden-yellow 
precipitate  is  formed. 

3.  With  alkali  hydroxides,  carbonates,  and  bicarbonates,  cincho- 
nine salts  form  white  precipitates  insoluble  in  ammonia. 

Cinchonidine,  C19H22N2O.  An  alkaloid  isomeric  with  cinchonine; 
soluble  in  75  times  its  weight  in  ether.  The  sulphate  is  official. 

A  mixture  of  equal  parts  of  sugar  and  cinchonidine  sulphate 
heated  in  a  dry  test-tube  causes  a  deposit  of  red  oily  drops  on  the 
cool  portion  of  the  tube.  The  addition  of  4  c.c.  of  a  saturated  aqueous 
solution  of  phenol  to  1  c.c.  of  a  saturated  aqueous  solution  of  cin- 
chonidine,  sulphate  causes  a  copious  deposit  of  small  crystals. 

Strychnine,  Strychnina,  C2,H22N2O2  =  334.  This  alkaloid  is 
found,  together  with  brucine,  in  the  seeds  and  bark  of  different 
varieties  of  Strychnos,  and  is  generally  obtained  from  nux  vomica. 
Strychnine  is  a  white,  crystalline  powder,  having  an  intensely  bitter 
taste,  which  is  still  perceptible  in  solutions  containing  1  in  700,000. 
It  is  nearly  insoluble  in  water  and  in  ether,  soluble  in  chloroform 
and  in  dilute  acids. 

By  dissolving  it  in  sulphuric  acid  the  official  strychnine  sulphate, 
Strychnine  sulphas,  (C21H22N2O2)2.H2SO4.5H2O,  is  obtained. 

Strychnine  has  strong  basic  properties  and  is  one  of  the  most  power- 
ful poisons  known,  one-quarter  of  a  grain  having  caused  death  within 
a  few  hours. 

Analytical  reactions : 

1.  Strychnine  dissolves  in  sulphuric  acid  and  nitric  acid  without 
color. 

2.  A  fragment  of  potassium  dichromate,  drawn  through  a  solution 
of  strychnine  in  concentrated  sulphuric  acid,  produces  momentarily  a 
blue,  then  brilliant  violet  color,  which  slowly  passes  to  cherry-red, 
then  to  rose-pink,  and  finally  to  yellow.     This  reaction  may  still  be 
noticed  with  50  j,06  grain  of  strychnine  (Plate  VII.,  5). 

3.  Sonnemchein's  test.     When  to  a  very  small  quantity  of  strych- 
nine, dissolved  in  a  drop  of  sulphuric  acid,  some  ceroso-ceric  oxide  is 
added,  and  the  mixture  is  stirred  with  a  glass  rod,  a  deep-blue  color 


400  CONSIDERATION  OF  CARBON  COMPOUNDS 

is  produced,  changing  soon  to  violet,  and  finally  remaining  cherry- 
red.  One  part  of  strychnine  in  one  million  parts  of  water  can  thus 
be  recognized.  The  reagent  may  be  made  by  heating  cerium  oxalate 
to  redness  and  dissolving  it  in  30  times  its  weight  of  sulphuric 
acid. 

4.  Solutions  of  strychnine  give  with  diluted  solution  of  potassium 
dichromate  a  yellow,  crystalline  precipitate,  which,  when  collected, 
washed,  and  heated  with  concentrated  sulphuric  acid,  shows  the  play 
of  colors  described  in  test  2. 

5.  Neutral  solutions  of  strychnine  give  yellow  precipitates  with  the 
chlorides  of  gold  and  platinum  and  with  picric  acid  ;  a  white  precipi- 
tate with  mercuric  chloride,  potassium  hydroxide,  and  with  chlorine 
water ;  a  greenish-yellow  precipitate  with  potassium  ferrocyanide. 

If  to  the  last-named  precipitate,  after  careful  decantation  of  the 
liquid,  sulphuric  acid  is  added,  a  similar  play  of  colors  is  produced 
as  stated  in  reactions  2  and  3. 

Brucine,  C23H26N2O4.4H2O.  This  alkaloid  is  found  associated 
with  strychnine  in  various  species  of  Strychnos.  It  is  readily  soluble 
in  alcohol,  amyl  alcohol,  and  chloroform,  but  sparingly  soluble  in 
cold  water  and  in  ether. 

Analytical  reactions : 

1.  To  1  c.c.  of  water  add  5  drops  of  nitric  acid  and  5  milligrammes 
of  brucine  ;  a  deep  blood-red  color  results.     Heat  the  liquid  until  it 
has  assumed  a  yellow  color,  then  add  9  c.c.  of  cold  water  and  a  few 
milligrammes  of  sodium  thiosulphate  (or  a  small  crystal  of  stannous 
chloride);  a  beautiful  amethyst  or  violet  color  results  (Plate  VII., 6). 

2.  Fresh  chlorine  water,  added  drop  by  drop  to  a  concentrated 
brucine  solution,  produces  a  red  color,  turning  violet,  and  becoming 
colorless  on  addition  of  an  excess  of  chlorine. 

Atr opine,  Atropina,  CI7H23NO3  =  289  (Daturine).  Occurs  in 
Atropa  belladonna.  It  is  a  white,  crystalline  powder,  having  a  bitter 
and  acrid  taste  and  an  alkaline  reaction  ;  it  is  sparingly  soluble  in 
water,  but  very  soluble  in  alcohol  and  chloroform.  Atr  opine  sulphate, 
(C17H23NO3)2.H2SO4,  is  a  white,  crystalline  powder,  easily  soluble  in 
water. 

Analytical  reactions: 

1.  Atropine  dissolves  in  concentrated  sulphuric  acid  without  color. 

2.  The  above  solution  is  not  colored  by  nitric  acid  (difference  from 
morphine),  and  not  at  once  by  potassium  dichromate  (difference  from 


ALKALOIDS.  401 

strychnine).     Prolonged  contact  with  potassium  dichromate  causes 
the  solution  to  turn  green. 

3.  The  green  solution  obtained  by  the  action  of  potassium  dichro- 
mate upon  atropine  which  has  been  dissolved  in  sulphuric  acid, 
evolves  on  the  addition  of  a  few  drops  of  water  and  warming,  a 
pleasant  odor  reminding  of  roses  and  orange  flowers.     A  similar 
odor  may  be  noticed  when  a  fragment  of  atropine  is  heated  slowly 
in  a  dry  test-tube  until  it  fuses  and  white  fumes  begin  to  appear, 
heating  this  mass  with  a  few  drops  of  concentrated  sulphuric  acid 
until  it  commences  to  turn  brown,  and  then  adding  at  once,  but  care- 
fully, about  two  volumes  of  water. 

4.  Solutions  of  atropine  dilate  the  pupil  of  the  eye  to  a  marked 
extent. 

5.  One  milligramme  of  atropine,  mixed  well  with  an  equal  weight 
of  sodium  nitrate  and  3  drops  of  sulphuric  acid,  gives  a  yellowish- 
red  mixture,  which  turns  violet  on  adding  5  milligrammes  of  pow- 
dered sodium  hydroxide  and  a  drop  of  alcohol. 

Hyoscyamine,  C17H23NO3.  Found  in  small  quantities  together 
with  hyoscine  in  the  seeds  of  Hyoscyamus  niger  (henbane),  and  in 
some  other  plants  belonging  to  the  solanaceae. 

Hyoscyamine  resembles  atropine  closely  in  most  of  its  chemical, 
physical,  and  physiological  properties,  but  the  corresponding  salts  of 
the  two  alkaloids  crystallize  in  different  forms ;  the  hydrobromate 
and  sulphate  are  official. 

Hyoscyamine  differs  from  atropine  by  yielding  with  gold  chloride 
a  precipitate  which,  when  recrystallized  from  a  hot  aqueous  solution, 
acidified  with  hydrochloric  acid,  deposits  lustrous,  golden-yellow 


Hyoscine,  C17H21NO4.  Found  together  with  hyoscyamine  in 
Hyoscyamus.  The  alkaloid  is  known  only  in  an  amorphous,  semi- 
solid  state,  but  the  salts,  of  which  the  hydrobromate  is  official,  crys- 
tallize readily.  Hyoscine  evaporated  to  dryness  on  a  water-bath 
with  a  few  drops  of  fuming  nitric  acid  leaves  a  nearly  colorless 
residue  which  turns  violet  on  the  addition  of  some  alcoholic  solution 
of  potassium  hydroxide. 

Cocaine,  C17H21NO4.  This  alkaloid  is  found  in  the  leaves  of  the 
South  American  shrub  Erythroxylon  coca  in  quantities  varying  from 
0.15  to  0.65  per  cent.  It  is  a  white,  crystalline  powder,  soluble  in 
about  700  parts  of  water,  easily  soluble  in  alcohol,  ether,  and  chloro- 

26 


402  CONSIDERATION  OF  CARBON  COMPOUNDS. 

form ;  it  fuses  at  98°  C.  (208°  F.).  A  fragment  of  cocaine  placed 
on  the  tongue  causes  the  sensation  of  numbness  without  acrid  or 
bitter  taste  ;  the  solution  in  water  is  faintly  bitter. 

Cocaine  heated  with  acids  in  sealed  tubes  is  decomposed  into  methyl  alcohol, 
benzoic  acid,  and  ecgonine,  showing  it  to  be  methyl-benzoyl-ecgonine : 

C12H21N04  +  2H20  =  CH3HO  +  C7H5CO2H  +  C9H15NO3. 
Cocaine.  Methyl  alcohol.   Benzoic  acid.          Ecgonine. 

Ecgonine  is  found  in  the  coca  leaves  as  benzoyl-ecgonine,  C9H15(C7H50)NO3 
+  4H2O ;  this  is  a  white,  crystalline  substance  from  which  cocaine  may  be 
obtained  by  heating  it  with  methyl-iodide.  The  mother-liquors  obtained  in 
the  manufacture  of  cocaine  from  the  leaves  contain  the  alkaloid  in  an  amor- 
phous state  and  possibly  one  or  two  other  alkaloids,  one  of  which  has  been 
named  hygrine.  Whether  these  alkaloids  are  contained  in  the  coca-plant,  or 
are  products  of  the  decomposition  of  cocaine,  are  questions  not  yet  decided. 

Of  the  various  salts  of  cocaine,  the  hydrochlorate,  C17H21NO4. 
HC1,  has  been  used  chiefly.  This  salt  crystallizes  from  alcohol  in 
short,  anhydrous  prisms,  from  an  aqueous  solution,  however,  with 
two  molecules  of  water,  which  are  completely  expelled  at  a  temper- 
ature of  100°  C.  (212°  F.).  The  anhydrous  salt  fuses  at  193°  C. 
(379°  F.)  and  is  readily  soluble  in  water ;  this  salt  solution  has  a 
somewhat  more  bitter  taste  than  the  alkaloid  itself. 

Analytical  reactions : 

1.  Cocaine  salts  are  precipitated  from  an  aqueous  solution  as  fol- 
lows :  Platinum  chloride  produces  a  yellowish-white,  mercuric  chlo- 
ride a  white  flocculent,  picric  acid  a  yellow  pulverulent,  the  alkali 
carbonates  and  hydroxides  a  white  precipitate,  which  latter  is  soluble 
in  ammonia. 

2.  To  a  freshly  prepared  solution  of  potassium  ferricyanide  add 
an  equivalent  amount  of  ferric  chloride;  with  this  solution  of  ferric 
ferricyanide  moisten  a  slip  of  filter-paper  and  place  on  this  a  drop  of 
cocaine  solution.     A  deep-blue  spot  of  ferric  ferrocyanide  will  appear 
shortly  in  consequence  of  the  deoxidizing  action  of  the  alkaloid  upon 
the  ferricyanide.     (Morphine,  a  few  other  alkaloids,  and  many  re- 
ducing agents  show  the  same  reaction.) 

3.  Boil  a  small  quantity  of  cocaine  solution  for  a  few  minutes  with 
dilute  sulphuric  acid;  neutralize  carefully  with  potassium  hydroxide 
and  then  add  a  few  drops  of  ferric  chloride  solution.  A  pale  brownish- 
yellow  precipitate  of  basic  ferric  benzoate  will  form. 

Aconitine,  C33H45N012  ?  This  alkaloid  is  found  in  various  species  of  aco- 
nitum  to  the  amount  of  about  0.2  per  cent.  The  commercial  article  is  most 
likely  a  mixture  of  aconitine  with  other  substances,  as  it  is  extremely  difficult 


ALKALOIDS.  403 

to  obtain  the  alkaloid  in  an  entirely  pure  form ;  the  composition  given  above 
corresponds  to  the  analysis  of  the  purest  obtainable  article.  Aconitine  is  one 
of  the  most  poisonous  substances  known;  there  are  no  reliable  chemical  tests 
by  which  it  may  be  readily  distinguished  from  other  alkaloids ;  the  aqueous 
solution  is  precipitated  by  alkalies,  tannic  acid,  Mayer's  reagent,  and  solution 
of  iodine  in  potassium  iodide,  but  not  by  platinic  chloride,  mercuric  chloride, 
and  picric  acid.  Characteristic  is  the  intensely  acrid  taste  of  the  alkaloid  and 
the  numbness  and  tingling  caused  by  it  in  the  mouth  and  throat.  The  greatest 
care  should  be  exercised  in  examining  aconitine  for  these  properties. 

Veratrine,  Veratrina.  This  is  a  mixture  of  alkaloids  obtained 
from  the  seed  of  Asagrsea  officinalis.  It  is  a  white,  amorphous,  rarely 
crystalline  powder,  highly  irritating  to  the  nostrils  ;  nearly  insoluble 
in  water,  readily  soluble  in  alcohol. 

Analytical  reactions  : 

1.  Concentrated  sulphuric  acid  causes  with  veratrine  first  a  yellow, 
then   reddish-yellow,   intense  scarlet,  and,  finally,  violet-red  color. 
(Plate  VII.,  8.)     The  yellow  or  orange-red  solution  exhibits,  by 
reflected  light,  a  greenish  fluorescence. 

2.  Veratrine,  when  heated  with  concentrated  hydrochloric  acid, 
dissolves  with  a  blood-red  color. 

3.  Bromine  water  colors  veratrine  violet. 

4.  Veratrine  forms  with  nitric  acid  a  yellow  solution. 

Hydrastine,  C21H21N06.  Found  together  with  berberine  in  the  rhizome  of 
hydrastis  Canadensis  (golden  seal)  in  quantities  varying  from  0.1  to  0.2  per 
cent.  Hydrastine  crystallizes  in  four-sided,  colorless  prisms ;  it  fuses  at  132°  C. 
(270°  F.),  is  insoluble  in  water  and  benzin,  soluble  in  about  2  parts  of  chloro- 
form, 83  parts  of  ether,  and  120  parts  of  alcohol  at  the  ordinary  temperature. 

Hydrastine  answers  to  all  the  general  tests  for  alkaloids;  treated  with  con- 
centrated sulphuric  acid  it  shows  a  yellow  color,  turning  red,  then  purple  on 
heating.  Concentrated  nitric  acid  produces  a  yellow  color,  changing  to  orange. 
The  fluorescence  noticed  in  solutions  of  hydrastine  or  its  salts  is  due  to  pro- 
ducts formed  from  it  by  oxidation.  While  hydrastine  itself  crystallizes  very 
readily,  especially  from  solutions  in  acetic  ether,  its  salts  can  scarcely  be 
obtained  in  crystals. 

Hydrastinine,  CUHUNO2.  When  hydrastine  is  treated  with 
oxidizing  agents  it  is  converted  into  hydrastinine,  the  hydrochlorate 
of  which  is  official.  This  salt  has  a  pale-yellow  color,  a  bitter,  saline 
taste,  and  is  soluble  in  0.3  part  of  water,  and  also  readily  soluble  in 
alcohol,  but  difficultly  soluble  in  ether  or  chloroform.  A  dilute 
aqueous  solution  of  the  salt  (up  to  about  1  in  100,000)  has  a  decided 
blue  fluorescence. 


404  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Berberine,  C,0H17N04.  Found  in  a  number  of  plants  (berberis  vulgaris, 
hydrastis  Canadensis,  etc.)  belonging  to  entirely  different  families.  It  is  a 
yellow,  crystalline  substance,  soluble  in  7  parts  of  alcohol,  18  parts  of  water, 
insoluble  in  ether,  chloroform,  and  benzene. 

Berberine  not  only  forms  well-defined,  readily  crystallizing  salts  with  acids, 
but  it  also  enters  into  combination  with  a  number  of  other  substances,  as,  for 
instance,  with  alcohol,  ether,  chloroform,  etc.  Some  of  these  compounds  crys- 
tallize well,  as  for  instance,  berberine-chlorotorm,  C20H17N04.CHC13. 

Physostigraine,  C15H21N3O2  (Eserine).  Found  in  the  seeds  of 
Physostigma  venenosum  (Calabar  bean).  The  pure  alkaloid  does  not 
crystallize  well,  is  almost  tasteless,  and  assumes  gradually  a  reddish 
tint.  The  sulphate  and  salicylate  are  official.  Both  are  white  or 
yellowish-white  crystalline  powders,  which  have  a  bitter  taste.  The 
sulphate  is  readily,  the  salicylate  sparingly  soluble  in  water. 

Analytical  reactions: 

1.  Five   milligrammes   of   physostigmine   dissolved  in  2c.c.    of 
ammonia  water  yield  a  yellowish-red  liquid  which,  on  evaporation 
on  a  water-bath,  leaves  ,a  blue  or  bluish -gray  residue,  soluble  in 
alcohol,  forming  a  blue  solution.     Upon  supersaturation  with  acetic 
acid  this  becomes  violet  and  exhibits  a  strong  reddish  fluorescence. 
The  violet  solution  leaves  on  evaporation  a  residue  which  is  first 
green  and  afterward  blue.     (Plate  VII.,  7.) 

2.  Physostigmine  or  its  salts  give  with  calcium  oxide  and  water  a 
red  liquid,  which  turns  green  on  heating. 

Pilocarpine,  CnH16N202.  Found  in  the  leaflets  of  Pilocarpus  Selloanus.  The 
alkaloid  crystallizes  with  difficulty ;  its  solutions  in  ether,  alcohol,  or  water 
have  an  alkaline  reaction.  The  hydrochlorate  is  official.  It  is  a  white,  crys- 
talline powder,  which  dissolves  in  fuming  nitric  acid  with  a  faintly  greenish 
tint.  The  aqueous  solution  is  precipitated  by  most  of  the  common  reagents  for 
alkaloids. 

Caffeine,  Caffeina,  C8H10N4O2.H2O  =  212  (Trimethyl-xanthine, 
Theine,  Guaraniri),  occurs  in  coffee,  tea,  Paraguay  tea,  and  a  few 
other  plants.  It  forms  fleecy  masses  of  long,  flexible,  silky  needles, 
which  are  soluble  in  80  parts  of  water  and  in  33  parts  of  alcohol ; 
it  has  a  slightly  bitter  taste  and  a  neutral  reaction. 

Caffeine  and  theobromine  show  the  properties  of  alkaloids  to  a 
much  less  degree  than  the  majority  of  the  compounds  considered  in 
this  chapter ;  they  do  not  act  on  red  litmus  and  are  but  feebly  basic. 

Citrated  caffeine  U.  S.  P.  is  obtained  by  adding  caffeine  to  a  solu- 
tion of  citric  acid  and  evaporating  the  mixture  to  dry  ness. 

Caffeine  is  dissolved  by  sulphuric  acid  without  color ;  when  treated 


ALKALOIDS.  405 

with  strong  nitric  acid  it  forms  a  yellow  liquid  which,  after  evapora- 
tion, assumes  a  purplish  color  when  moistened  and  carefully  heated 
with  water  of  ammonia. 

Two  volumes  of  a  saturated  solution  of  caffeine  in  water  mixed 
with  one  volume  of  mercuric  chloride  solution  form  after  a  short 
time  large  crystals  of  caffeine-mercuric  chloride. 

Theobromine,  C7H8N4O2  (Dimethyl-xanihine).  Found  in  the  seeds 
of  Theobroma  cacao,  a  tree  growing  in  the  tropics.  It  is  white,  crys- 
talline, sparingly  soluble  in  cold  water,  alcohol,  and  ether,  volatilizes 
without  decomposition  at  290°  C.  (554°  F.),  has  a  neutral  reaction, 
but  forms  with  acids  well-defined  salts.  * 

Theobromine  has  been  obtained  from  xanthine,  C5H4N4O2  (a  base  found  in 
animal  liquids),  by  treating  its  lead  compound  with  methyl-iodide,  CH3I,  when 
lead  iodide  and  dimethyl-xanthine  are  formed.  By  introducing  a  third  methyl 
group  into  the  molecule  of  theobromine  trimethyl-xanthine,  i.  e.,  caffeine  or 
theine  is  formed.  These  facts  show  the  close  relationship  between  the  active 
principles  of  the  vegetable  substances  used  so  extensively  in  the  preparation 
of  the  beverages,  coffee,  tea,  and  chocolate.  And  again,  these  principles  show 
a  relationship  to  a  series  of  substances  (such  as  xanthine,  uric  acid,  and  others) 
which  are  found  in  animal  fluids. 

Piperin,  C17H19NO3.  This  compound  is  found  in  black  and  white 
pepper.  While  it  is  isomorphous  with  morphine,  it  differs  widely 
from  it  in  all  its  properties.  It  can  hardly  be  called  an  alkaloid,  as 
it  has  no  alkaline  reaction,  is  but  feebly  basic  and  does  not  show  the 
general  alkaloidal  reactions.  It  forms  colorless,  or  pale  yellowish 
crystals  which  are,  when  first  put  in  the  mouth,  almost  tasteless,  but 
produce  on  prolonged  contact  a  sharp  biting  sensation. 

Piperin  dissolves  in  concentrated  sulphuric  acid  with  a  dark  blood- 
red  color,  which  disappears  on  dilution  with  water.  Treated  with 
nitric  acid  it  turns  rapidly  orange,  then  red. 

Ptomaines  (Putrefactive  or  cadaveric  alkaloids).  It  has  been 
known  for  a  long  time  that  vegetable,  and  more  especially  animal 
matter,  when  in  a  state  of  decomposition  (putrefaction)  acts  generally 
as  a  poison,  both  when  taken  as  food  or  when  injected  under  the  skin. 
Though  many  attempts  had  been  made  to  isolate  the  poisonous  pro- 
ducts, this  was  not  accomplished  successfully  until  the  years  1873  to 
1876,  by  Francesco  Selmi,  of  Italy.  He  demonstrated  that  a  great 
number  of  basic  substances  can  be  extracted  from  putrid  matter  by 
treating  it  successively  with  ether,  chloroform,  amyl  alcohol,  and 


406  CONSIDERATION  OF  CARBON  COMPOUNDS. 

other  solvents.  He  also  showed  that  these  substances  resemble  vege- 
table alkaloids  in  many  respects,  and  assigned  to  them  the  name 
ptomaines,  derived  from  7rr«//a,  that  which  is  fallen — i.  e.,  a  cadaver. 
Although  Selmi  did  not  succeed  in  isolating  any  of  the  ptomaines 
completely  (he  experimented  with  extracts  only)  his  investigations 
stimulated  other  scientists,  and  by  the  united  eiforts  of  many  workers 
our  knowledge  of  ptomaines  has  now  advanced  so  far,  that  general 
statements  can  be  given  in  regard  to  their  origin,  composition,  phys- 
ical and  chemical  properties,  action  upon  the  animal  system,  etc. 

Formation  of  ptomaines.  It  has  been  shown  in  Chapter  39  that 
albuminous  substances  under  favorable  conditions  undergo  a  decom- 
position termed  putrefaction.  Presence  of  moisture,  a  suitable  tem- 
perature, '  and  the  action  of  a  ferment  are  the  essential  factors  in 
putrefaction.  The  ferments  are  living  organized  beings,  termed 
germs,  bacteria,  bacilli,  microbes,  organized  ferments,  etc. 

It  is  during  the  growth,  development,  and  multiplication  of  these 
micro-organisms  that  the  decomposition  of  the  albuminous  sub- 
stances into  simpler  forms  of  matter  takes  place.  A  full  explanation 
of  the  exact  mode  of  the  formation  of  decomposition-products  from 
organic  matter  by  the  action  of  bacteria  has  not  been  furnished  yet, 
but  we  do  know  that  ptomaines  are  found  among  these  products. 
We  also  know  that  certain  bacteria  split  up  organic  molecules  in  a 
certain  direction,  i.  e.,  with  the  formation  of  certain  products.  We 
also  know  that  while  micro-organisms  live  chiefly  in  dead  organic 
matter,  they  also  have  the  power  of  existing  and  multiplying  in  the 
living  organism,  causing  the  decomposition  of  living  tissues,  often 
with  the  formation  of  ptomaines. 

General  properties  of  ptomaines.  Ptomaines  resemble  veg- 
etable alkaloids  in  all  essential  properties.  Some  contain  carbon, 
hydrogen,  and  nitrogen  only,  corresponding  to  the  volatile  alkaloids, 
such  as  coniine  and  nicotine,  while  others  contain  oxygen  also,  corre- 
sponding to  the  fixed  alkaloids. 

Ptomaines  and  alkaloids  both  have  the  basic  properties  and  the 
power  to  combine  with  acids  to  form  well-defined  salts ;  they  have  in 
common  a  number  of  characteristic  reactions,  such  as  the  formation  of 
precipitates  with  the  chlorides  of  platinum,  mercury,  gold,  as  also 
with  tannic  acid,  phospho-molybdic  acid,  picric  acid,  etc. ;  and  both 
show  corresponding  solubility  and  insolubility  in  the  various  solvents 
generally  used  for  the  extraction  of  alkaloids. 


ALKALOIDS.  407 

Ptomaines  not  only  possess  the  general  characters  of  true  alka- 
loids, bat  even  the  often  highly  characteristic  color-tests  of  the  latter 
are  in  some  cases  almost  identical  with  those  of  ptomaines.  Thus, 
ptomaines  have  been  found  which  resemble  in  their  chemical 
properties  as  well  as  in  their  physiological  action  upon  the  animal 
system,  the  alkaloids  morphine,  atropine,  strychnine,  coniine,  digi- 
tal ine,  etc. 

Many  attempts  have  been  made  to  find  some  characteristic  prop- 
erties by  which  to  differentiate  between  the  putrefactive  and  the 
vegetable  alkaloids,  but  practically  without  results.  It  is  true  that 
most  vegetable  alkaloids  are  optically  active,  while  ptomaines  are 
inactive,  but  it  does  not  often  happen  that  ptomaines  are  obtained  in 
such  quantities  as  to  permit  of  an  exact  determination  of  optical 
properties. 

Under  these  conditions  it  is  evident  that  the  toxicologist  has  a  most 
difficult  task,  when  called  upon  to  examine  a  body  (especially  when 
already  in  a  state  of  decomposition)  for  alkaloidal  poisons.  How 
many  times,  in  former  years,  chemists  may  have  unjustly  claimed  the 
presence  of  poisonous  vegetable  alkaloids  in  material  given  them  for 
examination,  we  cannot  say,  but  we  do  know  of  a  number  of  cases 
of  recent  date  in  which  such  claims  were  shown  to  be  based  upon 
errors,  made  in  consequence  of  the  close  analogy  between  ptomaines 
and  alkaloids. 

While  the  poisonous  properties  of  some  ptomaines  are  well  marked, 
others  are  more  or  less  inert.  The  poisonous  ptomaines  are  now 
often  termed  toxines,  in  order  to  distinguish  them  from  the  inert 
basic  products  of  putrefactive  changes. 

The  toxines  are  of  special  interest  to  the  physician,  because  it  is 
now  assumed  that  infectious  diseases  are  caused  by  the  poisonous 
products  formed  by  the  growth,  multiplication,  and  degeneration  of 
micro-organisms  in  the  living  body. 

The  great  likelihood  of  this  statement  is  of  far-reaching  impor- 
tance, as  it  opens  a  new  field  for  investigation  in  connection  with  the 
treatment  of  infectious  diseases. 

Non-poisonous  ptomaines.  A  number  of  these  basic  substances 
have  been  known  for  a  long  time.  Some  of  them  are  also  formed  by 
other  processes  than  those  of  putrefaction,  and  the  term  ptomaines 
may,  therefore,  not  well  be  chosen  for  all  of  them.  However,  the 
close  relationship  between  these  substances  unites  them  into  a  natural 
group,  of  which  the  following  members  may  be  mentioned : 


408  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Methylamine,  NH2.CH3,  the  simplest  organic  base  that  can  be  formed,  has 
been  found  in  decomposing  herring,  pike,  haddock,  poisonous  sausage,  cultures 
of  comma  bacillus  on  beef-broth,  etc.  It  is  an  inflammable  gas  of  strong  ain- 
moniacal  odor. 

Dimethylamine,  NH(CH3)2,  has  been  found  in  putrefying  gelatin,  decom- 
posing yeast,  poisonous  sausage,  etc.  It  is,  like  the  former,  a  gas  at  ordinary 
temperature. 

Trimethylamine,  N(CH3)3,  has  been  shown  for  a  long  time  to  occur  in  some 
animal  and  vegetable  tissues.  Its  presence  has  been  demonstrated  in  leaves 
of  chenopodium,  in  the  blood  of  calves,  in  human  urine,  etc.,  but  it  also  occurs 
as  a  product  of  putrefaction  in  yeast,  meat,  blood,  ergot,  etc.  It  is  a  liquid, 
possessing  a  strong,  fish-like  odor.  Boiling-point  9°  C.  (48°  F.). 

Ethylamine,  NH2.C2H5;  Diethylamine,  NH.(C2H5)2;  Triethy famine,  N.(C2H5)3; 
Propylamine,  NH2.C3H7;  Neuridine,  C5N2HU,  are  other  non-poisonous  volatile 
ptomaines  belonging  to  the  amine  group,  while  of  the  non-volatile  amides 
may  be  mentioned :  Mydine,  C8HnNO ;  Pyocyanine,  CUHUN02 ;  Betaine,  C5H15 
NO3,  etc. 

Poisonous  ptomaines.  While  no  strict  line  of  demarcation  can 
be  drawn  between  poisonous  and  non-poisonous  substances,  the  fol- 
lowing list  of  ptomaines  embraces  those  which  cause  serious  dis- 
turbances when  brought  into  the  animal  system : 

Isoamylamine,  C5H13N,  a  colorless,  strongly  alkaline  liquid,  has  been  found 
in  putrefying  yeast  and  in  cod-liver  oil .  It  is  strongly  poisonous,  producing 
rigor,  convulsions,  and  death. 

Cadaverine,  C5HUN2,  occurs  very  frequently  in  decomposing  animal  tissues, 
and  seems  to  be  a  constant  product  of  the  growth  of  the  comma  bacillus, 
irrespective  of  the  soil  on  which  it  is  cultivated.  It  is  a  syrupy  liquid,  pos- 
sessing an  exceedingly  unpleasant  odor,  resembling  that  of  coniine.  The  sub- 
stances which  have  been  described  by  various  scientists  as  "  animal  coniine  " 
were  most  likely  cadaverine.  This  base  is  not  very  poisonous,  but  is  capable 
of  producing  intense  inflammation,  necrosis,  and  suppuration  in  the  absence  of 
bacteria. 

Neurine,  C5H13NO,  is  a  base  which  has  been  obtained  by  boiling  protagon 
with  baryta,  and  has  been  formed  by  synthetical  processes.  It  also  occurs, 
however,  frequently  in  decomposing  meat.  It  is  exceedingly  poisonous,  even 
in  small  doses.  Atropine  possesses  a  strong  antagonistic  action  toward  neurine, 
and  the  injection  of  even  a  small  quantity  is  sufficient  to  dispel  the  symptoms 
of  poisoning  by  neurine. 

Choline,  C5H15NO2,  has  been  found  in  animal  tissues,  in  a  number  of  plants 
(hops,  ergot,  Indian  hemp,  white  mustard,  etc.),  and  in  putrid  matters.  It  is 
much  less  poisonous  than  neurine. 

Mytilotoxine,  C6H15NO2,  is  the  poison  found  in  poisonous  mussels.  It  has  a 
strong  paralysis-producing  action,  resembling  curara  in  that  respect. 

Typhotoxine  CTH17NO2,  is  looked  upon  as  the  specific  toxic  product  of  the 
activity  of  Koch-Eberth's  typhoid  bacillus.  The  poison  throws  animals  into  a 
paralytic  or  lethargic  condition,  so  that  they  lose  control  over  the  muscles  and 


ALKALOIDS.  409 

fall  down  helpless.  Simultaneously  frequent  diarrhceic  evacuations  take  place, 
and  death  follows  in  from  one  to  two  days. 

Tetanine,  C13H30N2O4,  has  been  obtained  from  cultures  of  tetanus  microbes, 
from  the  amputated  arm  of  a  tetanus  patient,  and  from  the  brain  and  nerve 
tissues  of  persons  who  died  from  tetanus.  It  produces  in  animals  the  symp- 
toms characteristic  of  tetanus,  such  as  tonic  and  clonic  convulsions.  While 
mice  and  rabbits  are  strongly  affected  by  tetanine,  dogs  and  horses  seem  to  be 
but  slightly  susceptible  to  its  action. 

Mydatoxine,  C6H13N02,  has  been  obtained  from  human  internal  organs  which 
were  kept  for  four  months  at  a  temperature  varying  from — 9°  to  +  5°C.  (16° 
to  41°  F.).  It  is  an  alkaline  syrup,  which  does  not  possess  strong  toxic 
properties. 

Tyrotoxicon.  The  composition  of  this  highly  poisonous  ptomaine  has  not 
been  established  yet.  It  has  been  found  in  decomposing  milk,  in  poisonous 
cheese,  ice-cream,  and  cream-puffs. 

Spasmotoxine.  Composition  yet  unknown.  Obtained  from  cultures  of  the 
tetanus-germ  on  beef-broth.  Produces  violent  convulsions. 

Leucomaines.  The  basic  substances  formed  in  the  living  tissues 
by  retrograde  metamorphosis,  during  normal  life,  are  known  as  leuco- 
maines, in  contradistinction  to  the  ptomaines,  or  basic  products  of 
putrefaction.  To  the  group  of  leucomaines  belong  many  substances 
known  long  ago,  such  as  creatine,  creatinine,  xanthine,  guanine,  and 
others.  Most  of  these  bodies  are  non-poisonous,  but  some  have  been 
discovered  of  late,  possessing  strong  poisonous  properties.  The  more 
important  leucomaines  will  be  mentioned  in  the  physiological  part. 

Bacterial  proteids  or  toxalbumins.  Of  even  a  more  recent  date 
than  the  discovery  of  ptomaines  is  that  of  bacterial  proteids,  a  group 
of  substances  of  which  but  little  is  known  so  far.  They  are  formed 
by  the  action  of  micro-organisms  upon  albuminous  matter.  The 
isolation  of  these  substances  is  extremely  difficult,  because  they  differ 
but  little  in  solubility  or  other  physical  and  chemical  properties  from 
the  normal  proteids ;  and,  moreover,  they  decompose  so  readily  that 
they  may  disappear  during  the  process  of  analysis.  Some  of  the 
bacterial  proteids  show  the  Millon  and  bitiret  reactions  characteristic 
of  albuminous  substances ;  they  are  also  precipitated  by  tannic  acid, 
picric  acid,  and  mercuric  chloride. 

Of  bacterial  proteids  which  have  been  isolated  may  be  mentioned  the 
proteid  poison  of  diphtheria.  This  substance  has  been  obtained  as  a  white, 
amorphous  powder  from  cultures  of  the  Loeffler  diphtheria  bacillus.  The 
poisonous  properties  of  this  substance  are  very  intense,  as  0.2  milligramme 
suffices  to  kill  a  rabbit.  The  symptoms  produced  by  the  poison,  when  injected 
into  susceptible  animals,  are  identical  with  those  produced  by  inoculation, 
with  the  living  bacillus. 


410  CONSIDERATION  OF  CARBON  COMPOUNDS 

Other  poisonous  proteids  have  been  obtained  from  cultures  of  the  tetanus 
bacillus,  of  the  comma  bacillus  (found  in  cholera  patients),  of  the  Eberth 
bacillus  (found  in  typhoid-fever  patients),  and  from  micro-organisms  found  in 
the  intestines  and  stools  of  children  suffering  from  summer  diarrhoea.  The 
proteids  in  the  latter  case  are  highly  poisonous,  causing,  when  injected  under 
the  skin  of  dogs,  vomiting,  purging,  collapse,  and  death. 

Antitoxins.  After  an  infectious  disease  has  passed  over,  there  are 
present  in  the  system,  as  a  result  of  the  action  of  the  micro-organisms 
upon  the  tissues  of  the  body,  certain  substances  which  have  the 
power  of  protecting  the  individual  to  a  certain  extent  against  other 
attacks  of  the  same  disease.  These  bodies  are  known  as  antitoxins ; 
their  chemical  composition  is  yet  unknown.  By  some  they  are  con- 
sidered albumins,  by  others  globulins ;  still  others  claim  them  to  be 
nucleins. 

The  antitoxins  are  found  in  the  blood-serum  of  the  animals  which  have 
recovered  from  an  infectious  disease,  and  this  serum  may  be  utilized  in  the 
treatment  of  the  same  disease  in  other  individuals,  and  in  even  rendering 
immune  others  susceptible  to  that  disease.  (Blood-serum  therapy  of  Behring.) 

Practically,  animals  such  as  cows,  horses,  dogs,  goats,  are  rendered  highly 
immune  to  such  diseases  as  tetanus  and  diphtheria  by  injecting  them  with 
attenuated  cultures  of  the  micro-organisms  (causing  these  diseases)  or  their 
toxins,  and  then  with  gradually  increasing  doses  of  virulent  cultures  until  the 
animals  become  highly  refractory  to  these  diseases.  The  blood-serum  of  such 
animals  is  now  extensively  used  with  remarkable  success  in  the  treatment  of 
tetanus  and  diphtheria. 

51.   PEOTEIDS  (ALBUMINOUS  SUBSTANCES). 

Occurrence  in  nature.  Proteids  form  the  chief  part  of  the  solid 
and  liquid  constituents  of  the  animal  body  ;  they  occur  in  blood, 

QUESTIONS. — 491.  State  the  general  physical  and  chemical  properties  of 
alkaloids.  492.  Give  a  general  method  for  the  extraction  and  separation  of 
alkaloids  from  vegetables.  493.  Mention  the  chief  constituents  of  opium,  and 
explain  the  process  for  determining  the  percentage  of  morphine  in  opium. 

494.  Mention  the  properties  of  morphine  and  its  salts ;  give  tests  for  them. 

495.  Mention  the  principal  alkaloids  found  in  cinchona  bark,  and  give  a  pro- 
cess by  which  the  total  quantity  of  these  alkaloids  and  of  quinine  may  be 
determined.    496.  State  the  physical  and  chemical  properties  of  quinine  and 
cinchonine.     Which  of  their  salts  are  official,  and  by  what  tests  may  these 
alkaloids  be  recognized  and  distinguished  from  each  other?     497.  Give  tests  for 
strychnine,  brucine,  atropine,  and  veratrine.     498.  What  is  the  chemical  rela- 
tionship between  xanthine,  caffeine  and  theobromine  ?    499.  Mention  proper- 
ties of  and  give  tests  for  cocaine.     500.  Mention  the  characteristic  physical, 
chemical,  and  physiological  properties  of  ptomaines. 


PROTEIDS.  411 

tissues,  muscles,  nerves,  glands,  and  all  other  organs ;  they  are  also 
found  in  small  quantities  in  nearly  every  part  of  plants,  and  in  larger 
quantities  in  many  seeds.  They  have  never  yet  been  formed  by  arti- 
ficial means,  but  are  almost  exclusively  products  of  vegetable  life,  and 
undergo  but  little  change  when  consumed  as  food  and  assimilated  by 
animals. 

General  properties.  The  various  proteids  resemble  one  another 
closely  in  their  properties.  Their  composition  is  so  complex  that,  as 
yet,  no  chemical  formula  has  been  assigned  to  them  with  any  certainty, 
The  percentage  composition  and  other  reasons  have  led  to  a  formula 
represented  by  C144H224N36O44S2,  which  represents  about  the  average 
composition  of  the  proteids.  The  percentage  composition  is  shown  in 
the  following  figures  : 

Carbon 50.0  per  cent,  to  55.0  per  cent. 

Hydrogen       .        .        .        .        .      6.7       "        "      7.3       " 

Nitrogen 15.0       «        "    18.2       « 

Oxygen 20.0       "        "    24.0       " 

Sulphur 0.3       ""      2.5       " 

Of  other  properties  may  be  mentioned  : 

1.  They  are  amorphous,  colorless,  odorless,  nearly  tasteless  sub- 
stances, and,  with  the  exception  of  peptones,  incapable  of  dialysis. 

2.  They  are  not  volatile  without  decomposition. 

3.  They  easily  undergo  that  decomposition  known  as  putrefaction. 

4.  Some  are  soluble  in  water,  others  only  in   water  containing 
alkalies,  acids,  or  certain  neutral  salts,  whilst  some  are  insoluble. 

5.  The  soluble  proteids  are  converted  into  insoluble  modifications 
either  by  heating  to  60°  or  70°  C.  (140°  or  158°  F.),  or  by  the  addi- 
tion of  mineral  acids,  alcohol,  or  certain  metallic  salts.     This  process 
of  converting  soluble  into  insoluble  proteids  is  called  coagulation; 
and  proteids  when  once  coagulated  will  not  return  to  their  original 
soluble  form  without  suffering  some  alteration. 

6.  They  are  converted  into  peptones  by  the  action  of  gastric  juice. 
(See  later.) 

Analytical  reactions. 

(Use  a  solution  made  by  dissolving  some  of  the  white  of  an  egg  in  about 
10  parts  of  water,  and  filtering.) 

1.  Proteids  or  their  solutions  are  colored  yellow  by  warm  nitric 
acid  in  consequence  of  the  formation  of  a  substance  called  xantho- 
proteic  acid.  Addition  of  ammonia  water  changes  the  yellow  color 
to  orange  or  red. 


412  CONSIDERATION  OF  CARBON  COMPOUNDS. 

2.  Millorfs  reagent  colors  them  purple-red  on  heating.    This  reagent 
is  a  solution  of  mercuric  nitrate,  containing  some  excess  of  nitric  acid  ; 
it  is  best  made  by  dissolving  1  part  of  mercury  in  2  parts  of  nitric 
acid  of  a  specific  gravity  of  1.42,  and  diluted  with  2  volumes  of  water. 

3.  Biuret-reaction.     A  few  drops  of  dilute  cupric  sulphate  solution 
and  then  an  excess  of  potassium  hydroxide  added,  give  a  violet  color. 

4.  Heating  of  equal  volumes  of  proteid  solution  and  a  saturated 
aqueous  solution  of  ammonium  sulphate  causes  the  precipitation  of 
all  proteids  except  that  of  peptones. 

5.  A  few  drops  of  solution  of  1  part  of  cane  sugar  in  4  parts  of 
water  and  then  strong  sulphuric  acid  added,  produce  a  purple  color. 

6.  They  are  often  precipitated  by  highly  diluted  acids,  but  redis- 
solved  by  boiling  with  strong  hydrochloric  acid,  forming  a  violet-red 
solution.     The  precipitated  proteids  are  also  generally  dissolved  by 
caustic  alkalies. 

7.  They  are  also  precipitated  by  tannin,  carbolic  and  picric  acids, 
by  potassium  ferrocyanide  and  acetic  acid,  by  lead  acetate,  mercuric 
chloride,  and  by  most  salts  of  heavy  metals.     (The  use  of  egg-albu- 
min in  cases  of  poisoning  by  metallic  compounds  depends  on  this 
property.) 

Classification.  Our  present  unsatisfactory  state  of  knowledge 
regarding  proteids,  the  close  resemblance  which  they  show  in  prop- 
erties, and  the  difficulties  which  are  met  with  in  separating  them  in 
a  pure  state,  make  it  difficult  to  arrange  these  bodies  properly. 
However,  eight  classes  are  now  generally  distinguished.  They  are  : 
I.  Native  or  true  albumins  ;  II.  Globulins ;  III.  Derived  albumins 
or  albuminates ;  IV.  Fibrins ;  V.  Coagulated  proteids ;  VI.  Albu- 
moses ;  VII.  Peptones ;  VIII.  Amyloid  substance  or  Lardacein. 

Class  I.  Native  or  true  albumins.  These  proteids  are  soluble 
in  pure  water ;  the  solutions  become  turbid  at  60°  C.  (140°  F.),  and 
are  coagulated,  especially  in  presence  of  a  dilute  acid,  at  or  below  75°C. 
(167°  F.).  Strongly  alkaline  solutions  are  not  precipitated  by  heat- 
ing, and  the  presence  of  too  much  free  acid  may  also  prevent  coagula- 
tion. Coagulated  albumin  is  dissolved  by  strong  solutions  of  alkali 
hydroxides.  Native  albumins  occur  in  the  whites  of  birds7  eggs,  in 
milk,  in  the  plasma  of  the  blood,  chyle,  lymph,  etc.,  as  also  in  plants. 

a.  Serum-albumin  is  found  dissolved  in  blood-serum  (in  human 
blood  to  the  extent  of  about  4  to  5  per  cent.),  in  lymph,  chyle,  trans- 
udations,  and,  in  very  small  quantities,  in  milk.  Pathologically  it 


PROTEWS.  413 

occurs  in  urine.  Obtained  from  blood-serum  by  saturating  it  at 
30°  C.  (86°  F.)  with  magnesium  sulphate,  which  precipitates  globulin ; 
the  filtered  solution  is  saturated  at  40°  C.  (104°  F.)  with  sodium 
sulphate,  when  the  serum-albumin  is  precipitated.  Thus  obtained, 
it  is  not  quite  pure,  but  contains  some  salts  which  may  be  eliminated 
by  dissolving  the  precipitate  in  water  and  subjecting  the  solution  to 
dialysis. 

Pure  serum-albumin  is  an  almost  white,  or  pale-yellow,  elastic 
substance,  dissolving  readily  in  water  to  a  slightly  alkaline,  opales- 
cent solution,  which  coagulates  by  heating  to  50°  C.  (122°  F.),  while 
the  addition  of  sodium  chloride  raises  the  coagulating-point  to  75°- 
80°  C.  (167°-176°  F,).  It  is  not  readily  coagulated  by  alcohol  or 
precipitated  by  ether.  It  turns  the  plane  of  polarized  light  to  the  left. 

b.  Egg-albumin  differs  but  little  from  the  former,  but  may  be  dis- 
tinguished from  it  by  being  coagulated  by  ether,  which  does  not  affect 
serum-albumin.  It  exists  in  solution  in  the  white  of  eggs,  where  it 
is  contained  in  a  network  of  delicate  membranes. 

G.  Vegetable  albumin  exists  in  nearly  all  vegetable  juices,  and  is  a 
valuable  constituent  of  vegetables  used  as  food.  It  is  coagulated  at 
61°-63°  C.  (142°-146°  F.),  and  by  nearly  all  acids. 

Class  II.  Globulins.  They  are,  like  native  albumins,  coagulated 
by  heat,  but  differ  from  them  by  not  being  soluble  in  pure  water ; 
they  are  soluble  in  dilute  solutions  of  neutral  salts  of  the  alkalies  or 
alkaline  earths  (such  as  sodium  or  potassium  chloride,  sodium  or 
magnesium  sulphate,  etc.),  but  are  in  most  cases  precipitated  by 
saturated  solutions  of  the  salts  mentioned,  as  also  by  passing  a  cur- 
rent of  carbon  dioxide  through  their  solutions. 

a.  Paraglobulin  or  Serum- globulin.     This  substance  is  found  in 
considerable  quantity  in  blood-serum,  constituting  about  one-half  of 
its  total  proteids ;  it  also  occurs  in  lymph.     The  most  satisfactory 
method  of  preparing  paraglobulin  is  to  saturate  blood-serum  with 
magnesium  sulphate  at  a  temperature  of  30°  C.  (86°  F.),  when  it  is 
precipitated  and  purified  by  washing  it  upon  a  filter,  first  with  a  solu- 
tion  of  magnesium  sulphate,  and  then  with  water.     Paraglobulin 
shows  the  general  properties   mentioned  above  as  characteristic  of 
globulins. 

b.  Fibrinogen  is  the  name  given  to  a  substance  found  in  blood- 
plasma,  chyle,  lymph,  and  other  coagulable  fluids  of  the  body.     On 
contact  with  a  peculiar  ferment  (fibrin-ferment),  it  is  converted  into 
fibrin,  thereby  giving  rise  to  the  phenomenon  of  coagulation. 


414  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Fibrinogen  may  be  obtained  by  allowing  blood  to  run  directly 
from  the  vessels  into  a  weak  solution  of  magnesium  sulphate,  then 
separating  the  corpuscles,  and  precipitating  the  fibrinogen  by  satu- 
rating the  solution  with  sodium  chloride.  The  precipitate  is  collected 
on  a  filter  and  purified  by  dissolving  it  in  an  8  per  cent,  solution  of 
sodium  chloride,  and  reprecipitating  it  by  again  saturating  the  solu- 
tion with  the  salt. 

c.  Myosin.     Living  muscular  tissue  contains  a  yellowish,  opalescent 
fluid  (muscle-plasma),  which  filters  with  difficulty  and  clots  at  tem- 
peratures above  0°  C.  (32°  F.J.      This  clotting  or  coagulation  of 
muscle-plasma  also  takes  place  after  death  and  gives  rise  to  the  con- 
dition known  as  rigor  mortis.     This  change  is  similar  to  the  forma- 
tion of  fibrin  in  the  blood  and  possibly  due  to  the  action  of  a  myosin 
ferment. 

Myosin  is  obtained  by  extracting  muscular  tissue  with  10  per  cent, 
solution  of  ammonium  chloride  (in  which  it  is  readily  soluble)  and 
precipitating  it  from  this  solution  by  the  addition  of  large  quantities 
of  water. 

Aside  from  the  general  reactions  characteristic  of  globulins  it  is 
distinguished  by  the  low  temperature  of  40°  to  50°  C.  (104°  to  122° 
F.),  at  which  it  coagulates  when  dissolved  in  salt  solutions. 

d.  Orystallin  and  Vitellin  are  globulins  which  resemble  one  another 
so  closely  that  they  may  be  identical.    Crystallin  occurs  in  crystalline 
lenses  to  the  extent  of  nearly  25  per  cent. ;  vitellin  is  found  in  the 
yolk  of  hens'  eggs  to  the  amount  of  about  15  per  cent.     Both  sub- 
stances are  white,  flaky  solids,  readily  soluble  in  dilute  acids  and 
alkalies,  and  also  in  a  10  per  cent,  solution  of  sodium  chloride.    The 
latter  solution  is  coagulated  by  heating  to  75°  C.  (167°  F.). 

Class  III.  Derived  albumins  or  albuminates.  These  sub- 
stances are  insoluble  in  water,  and  in  dilute  neutral  salt  solutions ; 
soluble  in  dilute  acids  and  alkalies.  Solution  not  coagulated  on 
heating. 

a.  Acid-albumins.  When  the  solution  of  a  native  albumin,  such 
as  serum-  or  egg  albumin,  is  treated  for  some  little  time  with  a  dilute 
acid  (hydrochloric  acid)  its  properties  become  entirely  changed.  Thus : 
the  solution  is  no  longer  coagulated  by  heat,  and  on  neutralizing  it 
carefully  the  whole  of  the  albumin  is  precipitated.  This  shows  that 
the  native  albumin,  which  is  soluble  in  water  and  in  neutral  salt 
solutions,  has  been  changed  into  a  form  insoluble  in  these  agents,  and 
this  modified  form  is  termed  acid-albumin.  Acid-albumins,  while 


PEOTEIDS.  415 

insoluble  in  water  and  in  neutral  salt  solutions,  are  readily  dissolved 
by  dilute  acids,  and  also  by  diluted  alkaline  solutions,  most  likely 
with  conversion  into  alkali-albumins. 

6.  Syntonin  is  the  name  given  to  the  acid-albumin  obtained  by 
digesting  myosin  with  very  weak  (0.1  to  0.2  per  cent.)  hydrochloric 
acid.  From  the  solution  thus  formed  it  is  precipitated  by  neutraliz- 
ing with  an  alkali;  it  is  soluble  in  lime-water  and  in  dilute  solution 
of  sodium  carbonate.  Syntonin  represents  the  first  stage  in  the 
action  of  gastric  juice  upon  the  proteids.  It  is  a  pasty,  whitish  sub- 
stance, possessing  the  solubilities  mentioned  above  for  acid-albumins. 

c.  Alkali-albumins.     Obtained  by  treating   the   different  proteids 
with  alkalies  and  precipitating  the  solution  by  neutralizing  with  an 
acid.     They  resemble  acid-albumins  in  many  respects,  dissolve  very 
slightly  in  water,  neutral  salt  solutions,  and  also  in  lime-water. 

d.  Casein.     This  proteid,  which  resembles  alkali  albumin  closely, 
is  found  in  milk,  but  in  no  other  fluid  or  secretion  of  the  body.     It 
is  best  obtained  by  diluting  milk  with  about  4  volumes  of  water  and 
acidulating  the  mixture  with  acetic  acid  until  it  contains  about  0.1 
per  cent,  of  this  acid.     Casein  can  also  be  precipitated  from  milk  by 
the  addition  of  sodium  chloride  or  magnesium  sulphate. 

Pure  casein  is  a  fine,  snow-white  powder,  insoluble  in  water, 
soluble  in  alkalies,  carbonates,  and  phosphates  of  the  alkalies,  and  in 
lime-water.  From  these  solutions  it  is  precipitated  by  excess  of 
neutral  salts  (sodium  chloride)  and  by  dilute  acids,  an  excess  of  which 
redissolves  them.  It  is  not  coagulated  by  heat,  but  by  rennet,  an 
enzyme  found  in  gastric  juice. 

e.  Vegetable  casein  or  Legumin  occurs  in  considerable  quantities  in 
the  seeds  of  leguminosse,  such   as   peas   and  beans,  which   contain 
nearly  25  per  cent. ;  it  is  also  found  in  almonds,  various  nuts,  etc. 
It  shows  reactions  very  similar  to  milk-casein. 

Class  IV.  Fibrins.  Insoluble  in  water ;  soluble  with  difficulty 
in  strong  acids  and  alkalies,  and  undergoing  a  simultaneous  change 
into  members  of  Class  III.  Coagulated  by  heat. 

a.  Blood-fibrin  does  not  exist  as  such  in  the  body,  but  is  produced 
during  the  process  of  clotting  of  blood,  lymph,  chyle,  and  other  coag- 
ulable  fluids  of  the  body.  The  formation  is  due  to  the  action  of  the 
fibrin-ferment  (of  which  but  little  is  known)  upon  fibrinogen  and  pos- 
sibly a  second  substance,  fibrinoplastin.  It  may  be  obtained  unstained 
by  the  red  corpuscles  (as  it  is  in  a  common  blood-clot)  by  whipping 
fresh  blood  with  a  bundle  of  twigs  and  then  washing  with  water.  It 


416  CONSIDERATION  OF  CARBON  COMPOUNDS. 

is,  when  recently  obtained,  a  white,  gelatinous,  tenacious  mass,  con- 
sisting of  numerous  minute  fibrils.  When  dried  it  becomes  hard 
and  brittle.  It  is  insoluble  in  water,  alcohol,  and  ether,  but  swells 
up  and  dissolves  slowly  in  dilute  acids. 

b.  Vegetable  fibrin  or  Gluten  exists  in  many  parts  of  vegetables, 
and  is  best  obtained  from  wheat-flour  by  kneading  it  on  a  sieve  with 
water,  when  the  starch  passes  through  and  gluten  remains  as  a  soft, 
elastic  mass,  insoluble  in  water,  alcohol,  and  ether.  It  is  probably  a 
mixture  of  several  proteids. 

Class  V.  Coagulated  proteids.  These  are  formed  by  the  action 
of  heat,  acids,  alcohols,  etc.,  on  solutions  of  true  albumins  or  globu- 
lins. They  are  insoluble  in  water,  dilute  acids  and  alkalies,  as  also 
in  neutral  salt  solutions  of  any  strength.  In  fact,  they  are  soluble 
only  in  strong  acids  and  strong  alkalies,  when,  however,  a  destructive 
decomposition  takes  place.  Prolonged  contact  with  dilute  acids, 
especially  at  high  temperatures,  also  effects  a  partial  solution  with 
decomposition.  The  most  characteristic  property  of  coagulated  pro- 
teids is  that  they  readily  undergo  gastric  and  pancreatic  digestion. 

Class  VI.  Albumoses.  Intermediary  products  between  acid- 
albumins  and  the  peptones.  The  albumoses  are  at  least  three  in 
number :  protalbumose,  hetero-albumose  and  dextro-albumose.  The 
albumoses  are  precipitated  by  a  saturated  solution  of  ammonium  sul- 
phate, while  peptone  remains  in  solution.  All  are  soluble  in  dilute 
solution  of  sodium  chloride,  and  some  in  water.  They  differ  but 
slightly  from  one  another,  and  give  a  red  color  with  the  biuret  test. 

Class  VII.  Peptones.  These  are  the  products  of  the  action  of 
the  gastric  and  pancreatic  juices  upon  proteids  during  the  process  of 
digestion.  They  are  soluble  in  water,  acids,  alkalies,  salt  solutions, 
including  solution  of  ammonium  sulphate;  only  precipitated  by 
alcohol,  tannic  acid,  potassium  mercuric  iodide,  and  mercuric  chlo- 
ride. They  give  a  red  color  with  the  biuret  test.  Characteristic  is 
that  peptones  are  capable  of  dialysis,  or  of  diffusion  through  mem- 
branes, whilst  proteids  are  not. 

Class  VIII.  Amyloid  substance  or  Lardacein.  This  is  a 
pathological  product,  which  is  sometimes  found  in  severe  wasting 
diseases,  imparting  a  peculiar  translucent  appearance  to  the  tissues. 
Its  composition  is  that  of  the  proteids,  but  differs  from  them  in  being 


PRO  TE  IDS.  417 

colored  red  by  iodine,  violet  or  blue  by  iodine  and  dilute  sulphuric 
acid.     It  does  not  undergo  putrefaction  as  readily  as  other  proteids. 

Heemoglobin  (Hcemato-crystallin,  Hcemato-globulin).  This  substance 
is  the  coloring  agent  of  the  blood ;  it  resembles  the  proteids  in  many 
respects,  but  differs  from  them  in  being  crystallizable  and  in  con- 
taining iron.  Its  composition  has  been  found  to  correspond  to  the 
formula  C600H960N154O179FeS3. 

The  most  characteristic  feature  of  a  solution  of  haemoglobin  is  its 
power  of  absorbing  various  gases ;  it  absorbs  oxygen  in  considerable 
quantities,  thereby  assuming  a  bright-red  color,  but  gives  up  the 
oxygen  again  when  treated  with  deoxidizing  agents.  Accordingly, 
we  distinguish  between  common  or  reduced  haemoglobin  and  oxy- 
hsamoglobin ;  by  means  of  oxidizing  and  reducing  agents,  the  one 
body  can  readily  be  converted  into  the  other.  Solutions  of  oxy- 
haemoglobin  show  a  bright-red  or  scarlet  color,  those  of  haemoglobin 
are  much  darker  and  of  a  purple  tint. 

Upon  the  combination  of  oxygen  with  the  haemoglobin  of  the 
blood  in  the  lungs,  and  the  deoxidation  of  the  haemoglobin  by  the 
tissues,  depends  the  process  of  respiration,  which  will  be  spoken  of 
later. 

Haemoglobin  enters  into  combination  with  certain  other  gases — for 
instance,  carbonic  oxide,  nitrogen  dioxide,  and  hydrocyanic  acid — 
more  readily  than  with  oxygen,  and  the  poisonous  properties  of  these 
gases  are  due  largely  to  their  power  of  satisfying  the  affinities  of 
the  haemoglobin,  and  in  this  way  rendering  it  incapable  of  taking  up 
oxygen. 

Haemoglobin  is  soluble  in  water,  in  dilute  solutions  of  albumin,  of 
the  alkalies  and  their  carbonates,  and  in  sodium  or  ammonium  phos- 
phate. It  is  insoluble  in  strong  alcohol,  ether,  and  in  the  volatile 
and  fatty  oils.  With  the  spectroscope  both  oxyhaemoglobin  and 
reduced  haemoglobin  show  characteristic  absorption  bands. 

Haemoglobin  may  be  obtained  in  beautiful  red  crystals,  which 
differ  in  shape,  and  solubility  in  water,  according  to  the  species  of 
animal  from  whose  blood  they  are  obtained. 

Haemoglobin  may  be  decomposed  by  boiling  with  alcohol  (or  by 
other  agents)  into  albumin  and  a  substance  called  hcematin,  C34H35 
]S"4O5Fe,  which  is  soluble  in  acidified  alcohol.  Haematin  is  a  bluish- 
black  powder,  which  forms  with  hydrochloric  acid  a  crystalline 
compound,  hcemine,  which  fact  is  made  use  of  in  a  characteristic 
microscopical  test  for  the  presence  of  blood. 

27 


418  CONSIDERATION  OF  CARBON  COMPOUNDS. 

Proteolytic  or  Hydrolytic  ferments.  Enzymes.  Proteolysis 
is  the  change  effected  in  proteids  during  their  digestion,  and  as  this 
change  in  most  cases  is  accompanied  by  the  taking  up  of  water,  the 
terms  proteolytic  or  hydrolytic  ferments  are  used  for  the  substances 
causing  the  digestive  changes.  They  are  also  called  enzymes,  to 
distinguish  them  from  organized  ferments,  such  as  yeast  and  bacteria. 
The  composition  of  these  compounds  is  not  definitely  known,  but  is 
similar  to  that  of  proteids.  Enzymes  are  present  in  many  secretions 
and  are  produced  within  the  body.  They  are  soluble  in  water  and 
glycerin,  but  insoluble  in  alcohol.  They  act  only  in  the  presence  of 
water.  They  have  no  power  of  reproduction  and  are  apparently  not 
diminished  in  quantity  by  activity.  Each  ferment  acts  upon  certain 
groups  of  compounds,  causing  them  (in  most  cases)  to  take  up  a 
molecule  of  water. 

The  most  important  of  these  unorganized  hydrolytic  ferments 
are  ptyalin,  found  in  saliva ;  pepsin  and  rennet  ferment,  found  in 
gastric  juice;  amylopsin,  trypsin,  steapsin,  and  a  milk-curdling  ferment 
found  in  pancreatic  juice ;  invertin,  found  in  intestinal  juices ;  and, 
finally,  a  fibrin-forming  ferment,  found  in  coagulating  blood.  (Eor 
details  of  most  of  these  ferments,  see  next  chapter). 

Pepsin  is  one  of  the  active  principles  of  gastric  juice,  capable  of 
converting  albumin,  in  the  presence  of  hydrochloric  acid,  into  soluble 
peptones.  While  pure  pepsin  is  not  known,  a  number  of  preparations 
containing  more  or  less  of  this  ferment  are  sold  as  pepsin.  They  are 
obtained  by  different  processes  of  extraction  from  the  glandular  layer 
of  fresh  stomachs  from  healthy  pigs. 

Pepsin,  U.  S.  P.,  should  be  either  a  fine,  white,  or  yellowish -white, 
amorphous  powder,  or  consist  of  thin,  pale  yellow  or  yellowish, 
transparent  or  translucent  grains  or  scales.  It  should  be  capable  of 
digesting  not  less  than  3000  times  its  own  weight  of  freshly  coagu- 
lated and  disintegrated  egg-albumin.  Saccharated  pepsin,  U.  S.  P., 
is  a  mixture  of  10  parts  of  pepsin  and  90  parts  of  sugar  of  milk. 

Experiment  62.  Use  the  U.  S.  P.  process  for  the  valuation  of  pepsin,  as  fol- 
lows :  Prepare,  first,  the  following  three  solutions  :  A.  To  294  c.c.  of  water  add 
6  c.c.  of  diluted  hydrochloric  acid.  B.  In  100  c.c.  of  solution  A  dissolve  0.067 
gramme  of  the  pepsin  to  be  tested.  C.  To  95  c.c.  of  solution  A,  brought  to  a 
temperature  of  40°  C.  (104°  F.),  add  5  c.c.  of  solution  B.  The  resulting  100 
c.c.  of  liquid  will  contain  0.21  gramme  of  HC1,  0.00335  gramme  of  pepsin,  and 
98  c.c.  of  water. 

Keep  an  egg  in  boiling  water  for  fifteen  minutes  ;  rub  the  coagulated  albumin 
through  a  No.  30  wire  sieve,  place  10  grammes  of  this  albumin  in  a  200  c.c. 


PROTEIDS.  419 

fiask,  add  solution  C,  shake  well,  and  place  the  flask  in  a  water-bath,  or 
thermostat,  kept  at  a  temperature  of  38°  to  40°  C.  (100°  to  104°  F.)  for  six 
hours,  and  shake  it  gently  every  fifteen  minutes.  If,  at  the  expiration  of  that 
time,  the  albumin  should  have  disappeared,  leaving  at  most  only  a  few,  thin, 
insoluble  flakes,  then  the  dissolving  power  of  the  pepsin  examined  is  not  less 
than  3000. 

The  relative  proteolytic  power  of  pepsin,  stronger  or  weaker  than  that  de- 
scribed above,  may  be  determined  by  ascertaining,  through  repeated  trials,  how 
much  of  solution  B  made  up  to  100  c.c.  with  solution  A  will  be  required  to 
dissolve  10  grammes  of  albumin  under  the  conditions  given  above. 

Pancreatin,  U.  S.  P.  This  preparation  is  a  mixture  of  the 
enzymes  existing  in  the  pancreas  of  warm-blooded  animals,  and  is 
usually  obtained  from  the  fresh  pancreas  of  the  hog.  It  is  a 
yellowish,  or  grayish,  almost  odorless  powder,  soluble  in  water, 
insoluble  in  alcohol.  It  has  the  power  to  digest  proteids,  and  to 
convert  starch  into  sugar. 

If  there  be  added  to  100  c.c.  of  water  contained  in  a  flask,  0.28  gramme  of 
pancreatin  and  1.5  gramme  of  sodium  bicarbonate,  and  afterward  400  c.c.  of 
fresh  cow's  milk,  previously  heated  to  38°  C.  (100°  F.),  and  if  this  mixture  be 
maintained  at  the  same  temperature  for  thirty  minutes,  the  milk  should  be  so 
completely  peptonized  that,  if  a  small  portion  of  it  be  transferred  to  a  test-tube 
and  mixed  with  some  nitric  acid,  no  coagulation  should  occur. 

Gelatinoids.  To  this  group  belong  a  number  of  substances 
occurring  in  bones,  skins,  horns,  hair,  nails,  feathers,  etc.,  and 
having  generally  the  property  of  forming  a  jelly  with  water.  The 
organic  matter  in  bones,  usually  called  ossein,  contains,  besides  an 
albuminous  substance,  the  two  gelatinoids  collagen  and  gelatin,  an 
impure  mixture  of  which  forms  common  glue. 

QUESTIONS. — 501.  To  which  class  of  substances  is  the  term  proteids  applied, 
and  which  elements  enter  into  their  composition  ?  502.  By  what  processes  are 
proteids  formed  in  nature,  and  where  do  they  occur?  503.  State  the  general 
properties  of  proteids.  504.  How  are  proteids  acted  upon  by  heat,  nitric  acid, 
and  Millon's  reagent?  505.  Into  which  groups  may  proteids  be  classified,  and 
how  do  they  differ  from  each  other?  506.  Mention  some  native  albumins; 
state  where  they  are  found,  and  by  what  tests  they  are  characterized  ?  507. 
How  may  blood-fibrin  be  obtained  and  what  are  its  properties  ?  508.  State 
formation  and  characteristic  properties  of  peptones.  509.  What  elements  are 
found  in  haemoglobin,  where  does  it  exist,  and  what  are  its  characteristic 
properties  ?  510.  What  is  pepsin,  and  how  does  it  act  upon  proteids  ? 


VII. 
PHYSIOLOGICAL  CHEMISTRY 


52.  CHEMICAL  CHANGES  IN  PLANTS  AND  ANIMALS. 

General  remarks.  Physiological  chemistry  is  that  part  of 
chemistry  which  has  more  especially  for  its  object  the  various 
chemical  changes  which  take  place  in  the  living  organism  of  either 
plants  or  animals.  It  considers  the  chemical  nature  of  the  different 
substances  used  as  "  food,"  follows  up  the  changes  which  this  food 
undergoes  during  its  absorption  and  assimilation  in  the  organism, 
and  treats,  finally,  of  the  products  eliminated  by  it.  The  chemical 
changes  taking  place  in  the  organism  are  either  normal  (in  health)  or 
abnormal  (in  disease).  The  abnormal  products  formed  under  ab- 
normal conditions  are  generally  termed  "  pathological  "  products. 

Difference  between  vegetable  and  animal  life.  As  a  general 
rule,  it  may  be  stated  that  the  chemical  changes  in  a  plant  are  pro- 
gressive or  constructive,  in  an  animal  regressive  or  destructive.  That  is 
to  say,  plants  take  up  as  food  a  small  number  of  inorganic  substances 
of  a  comparatively  simple  composition,  convert  them  into  organic 
substances  of  a  more  and  more  complicated  composition  with  the 
simultaneous  liberation  of  oxygen,  whilst  animals  take  up  as  food 
these  organic  vegetable  substances  of  a  complex  composition,  assim- 
ilating them  in  their  system,  where  they  are  gradually  used  (burned 
up)  and  finally  discharged  as  waste  products,  which  are  identical  (or 
nearly  so)  with  those  substances  serving  as  plant  food. 

Plant  food.  Waste  products  of  animal  life. 

Carbon  dioxide.  Carbon  dioxide. 

Water.  Water. 

Ammonia,  NH3.  Urea,     CO(NH2)2.    • 

Nitrates,     MxNO3.  Urates,  MzC5H2N4O3- 

f  Calcium.  f  Calcium. 

Phosphates  >  ,  M  um  Phosphates  •,  ,   M         ium. 

Sulphates      -    of  Sulphates       -    of  > 


[  Potassium.  Chlorides  Potassium. 

(420) 


CHEMICAL  CHANGES  IN  PLANTS  AND  ANIMALS.  421 

Formation  of  organic  substances  by  the  plant.  As  shown  in 
the  preceding  table,  plants  take  up  the  necessary  elements  for  organic 
matter  from  a  comparatively  small  number  of  compounds.  All  carbon 
is  derived  from  carbon  dioxide ;  hydrogen  chiefly  from  water ;  oxygen 
from  either  of  the  two  substances  named,  as  well  as  from  the  various 
salts ;  nitrogen  either  from  ammonia,  or  from  nitrates  or  nitrites ; 
while  sulphur  and  phosphorus  are  derived  from  sulphates  and  phos- 
phates respectively.  These  substances  are  taken  into  the  plant  chiefly 
by  the  roots,  .the  assimilation  of  the  necessary  mineral  constituents 
being  facilitated  by  an  acid  secretion  (discharged  from  the  roots) 
which  has  a  tendency  to  render  these  salts,  present  in  the  soil  and 
surrounding  the  roots,  soluble. 

Water  having  absorbed  more  or  less  of  carbon  dioxide,  of  ammonia 
or  ammonium  salts,  and  of  nitrates,  phosphates,  and  sulphates  of 
potassium,  calcium,  etc.,  enters  the  plant  through  the  roots  by  a  simple 
process  of  diffusion,  and  is  carried  to  the  various  green  parts  of  the 
plant  (chiefly  to  the  leaves),  where,  under  the  influence  of  sunlight,  a 
chemical  decomposition  and  the  formation  of  new  compounds  take 
place,  the  liberated  oxygen  being  discharged  directly  through  the 
leaves  into  the  atmosphere. 

It  is  difficult  to  explain  fully  the  process  of  the  formation  of  highly  complex 
organic  compounds  in  the  plant,  because  we  know  so  little  in  regard  to  the 
intermediate  products  which  are  formed.  However,  it  is  fair  to  assume  that 
the  various  compounds  above  mentioned  as  plant  food  are  first  decomposed 
(with  liberation  of  oxygen)  in  such  a  manner  that  residues  or  unsaturated 
radicals  are  formed,  which  combine  together.  From  these  compounds,  pro- 
duced at  first,  more  complicated  ones  will  be  formed  gradually  by  replacement 
of  more  hydrogen,  oxygen,  or  other  atoms  by  other  residues. 

The  following  equations,  while  not  showing  the  various" radicals  and  inter- 
mediate compounds  formed,  may  illustrate  some  of  the  results  obtained  by  the 
plant  in  forming  organic  compounds : 

C02  +     H20  =  H2C03 

H2CO3  —  O  =  H2CO2  =  Formic  acid. 
2CO2  +     H2O  =  H2C205 

H2C205  —  O  =  H.,C.,04  =  Oxalic  acid. 
6CO2  +  6H20  =  C6H12018 

C6H12018  -  120  =  C6H1206  =  Glucose. 
10CO2  +  8H2O  =  C10H16028 

Ci0H16O28  —  28O  =  C10H16  =  Oil  of  turpentine. 
10C02  +  4H20  +  2NH3  =*  C]0H14O24N2 

C10HUO24N2  —  24O  =  C10HUN2  =  Nicotine. 

The  above  formulas  show  that  the  formation  of  organic  compounds  in  the 
plant  is  always  accompanied  by  the  liberation  of  oxygen,  and  it  may  be  stated, 
as  a  general  rule,  that  no  organic  substance  (produced  in  nature)  contains  a 


422  PHYSIOLOGICAL  CHEMISTRY. 

quantity  of  oxygen  sufficient  to  convert  all  carbon  into  carbon  dioxide  and  all 
hydrogen  into  water,  which  fact  also  explains  the  combustibility  of  all  organic 
substances. 

Why  it  is  that  the  living  plant  has  the  power  of  forming  organic  substances 
in  the  manner  above  indicated,  we  know  not,  and  we  know  very  little  even  in 
regard  to  the  means  by  which  the  living  cell  accomplishes  this  formation,  but 
we  do  know  that  sunlight  is  that  agent  the  action  of  which  is  indispensable  for 
the  plant  in  the  formation  of  more  complicated  organic  substances  from  simpler 
ones. 

Decomposition  of  vegetable  matter  in  the  animal  system. 
It  has  been  stated  above  that  the  process  of  chemical  decomposition 
taking  place  in  the  animal  system  is  chiefly  regressive  or  destructive, 
that  is  to  say,  the  substances  formed  in  the  plant  are  taken  into  the 
animal  system,  where  they  are  gradually  oxidized  by  the  inhaled 
atmospheric  oxygen,  thereby  being  converted  into  simpler  forms  of 
combination  which  are  finally  eliminated  as  waste  products. 

It  has  been  shown  above  how  a  molecule  of  glucose  which  is  formed  in  the 
plant  requires  not  less  than  6  molecules  of  carbon  dioxide,  and  the  same  num- 
ber of  molecules  of  water  for  its  formation,  6  molecules  of  oxygen  being 
eliminated.  A  molecule  of  glucose  taken  into  the  animal  system  undergoes  the 
reverse  process ;  by  combining  there  with  6  molecules  of  oxygen  it  is  converted 
into  6  molecules  of  carbon  dioxide  and  the  same  number  of  molecules  of  water, 
thus: 

C6H12O6    +     12O    ==    6CO2     +     6H20. 

Animal  food.  The  food  taken  by  animals  is  (beside  water  and  a 
few  of  its  mineral  constituents)  all  derived  from  vegetables,  but  it  is 
taken  from  them  either  directly  or  indirectly  ;  in  the  latter  case  it  has 
been  taken  previously  into  and  assimilated  by  other  animals,  as  in 
case  of  food  taken  in  the  form  of  meat,  milk,  eggs,  etc.  While  some 
animals  (herbivora)  feed  upon  vegetable,  and  some  (carnivora)  upon 
animal  food  exclusively,  others  are  capable  of  taking  and  assimilating 
either. 

The  fact  that  animal  food  is  derived  from  vegetable  matter,  renders 
it  superfluous  to  state  that  the  elements  taking  an  active  part  in  the 
formation  of  either  vegetable  or  animal  matter  are  identical.  Of  the 
total  number  of  69  elements,  only  14  are  found  as  necessary  con- 
stituents of  the  animal  body.  These  elements  are  carbon,  hydrogen, 
oxygen,  nitrogen,  sulphur,  phosphorus,  chlorine,  fluorine,  silicon,  cal- 
cium, magnesium,  sodium,  potassium,  and  iron.  A  few  other  elements, 
such  as  aluminum,  manganese,  copper,  etc.,  are  sometimes  found  in 
the  animal  system,  but  they  cannot  be  looked  upon  as  normal  or 
necessary  constituents. 


CHEMICAL  CHANGES  IN  PLANTS  AND  ANIMALS.  423 

The  various  kinds  of  animal  food  are  derived  chiefly  from  three 
groups  of  organic  substances,  viz.,  carbohydrates  (sugars,  starch,  etc.), 
fats,  and  albuminous  or  nitrogenous  substances.  The  inorganic  sub- 
stances, such  as  phosphates,  chlorides,  etc.,  required  by  the  animal  in 
the  construction  of  bones,  for  the  liberation  of  hydrochloric  acid  in 
the  gastric  j  uice,  etc.,  are  generally  found  as  constituents  of  various 
kinds  of  food  or  are  derived  from  drinking-water.  Milk  contains  all 
the  necessary  organic  or  inorganic  constituents ;  bread  is  rich  in  phos- 
phates, which  latter  are  also  found  in  smaller  or  larger  quantities  in 
nearly  all  kinds  of  vegetable  and  animal  food. 

Through  the  food  are  supplied  those  compounds  which  supply  the 
constituents  that  replace  the  exhausted  material  of  the  living  cells, 
and  by  chemical  changes  their  inherent  potential  energy  is  converted 
into  the  heat  of  the  body  and  into  the  kinetic  energy  used  in  work- 
ing the  living  mechanism.  Whilst  the  nitrogenous  substances  have 
primarily  the  task  of  continuously  replacing  the  wear  and  tear  of  the 
nitrogenous  tissues,  they  also  serve  to  keep  up  the  animal  heat  and 
consequently  the  involuntary  or  voluntary  motion. 

To  some  extent,  the  animal  body  may  be  regarded  as  a  complicated  machine, 
in  which  the  potential  energy,  supplied  by  the  food,  is  converted  into  actual 
energy  of  heat  and  mechanical  labor.  The  main  difference  is  that  in  our 
machines  the  fuel  serves  as  the  source  of  energy  only,  while  in  the  body  the 
food  is  mainly  changed  first  into  tissue  (thus  building  up  and  renewing  the 
body  constantly),  serving  as  fuel  afterward.  While  in  the  best  steam-engine 
only  one-tenth  of  the  fuel  is  utilized  as  mechanical  work,  over  one-fifth  of  the 
energy  of  the  food  is  realized  in  the  human  body. 

The  relative  proportions  in  which  the  two  kinds  of  food  are  taken 
by  animals  depend  upon  the  nature  of  the  animal  and  upon  its  par- 
ticular condition  of  existence. 

Below  are  given  in  column  A  the  daily  quantities  of  dry  food 
required  to  maintain  a  grown  person  in  good  health,  with  neither 
loss  nor  gain  in  weight,  while  the  figures  in  column  B  refer  to  the 
quantities  of  dry  food  for  a  working  man  of  average  height  and  weight. 

A.  B. 

Proteids 100  grammes.  130  grammes. 

Fats 100        "  85        " 

Carbohydrates         .        .        .        .240        "  400        " 

Inorganic  salts         ....       25         ".  30         " 

Water 2600        "  2600        " 

The  table  below  shows  that  900  grammes  (about  2  pounds)  of 
bread,  340  grammes  (f  pound)  of  lean  meat,  and  57  grammes  (2 


424 


PHYSIOLOGICAL  CHEMISTRY. 


ouDces)  of  butter  will  supply  the  quantities  of  solid  food  required  in 
a  day  by  an  active  laborer  : 


Bread  Lean  meat              Butter 

(900  grammes).  (340  grammes.)     (57  grammes). 

74  grammes.  66  grammes.     ... 

14        "  12        "            50  grammes. 
460 

22        "  17        " 


Bread,  meat, 
and  butter. 

140  grammes. 

76        " 
460        " 

39 


Proteids  ... 
Fats  ... 
Carbohydrates  . 
Inorganic  salts  . 

In  providing  a  diet,  it  must  be  borne  in  mind  that  the  digestibility 
of  a  food  is  more  a  measure  of  its  nutritive  value  than  its  elementary 
composition.  Different  foods  show  great  differences  in  the  rapidity 
and  completeness  with  which  they  are  absorbed.  Thus  eggs,  fresh 
meat,  white  bread,  and  butter  are  absorbed  and  assimilated  more 
readily  than  pork,  rye  bread^  potatoes,  green  vegetables,  and  bacon. 

The  relative  proportions  of  nitrogenous  and  non-nitrogenous  matter 
in  various  kinds  of  food  are  shown  in  the  following  table  : 


Nitro-       Non-nitro- 


Nitro- 


Non-nitro 


genous.        genous. 

genous. 

genous. 

Sweet  potatoes 

.     1 

17 

Pork        . 

1 

3 

Bice    . 

.     1 

12 

Fat  mutton 

1 

2.7 

Carrots        . 

.     1 

11 

Peas  (dried)    . 

1 

2.5 

Potatoes 

.     1 

10 

White  beans   . 

1 

2.3 

Bread  . 

.     1 

5.0-6.8 

Milk        . 

1 

2.2 

Flour  . 

.    1 

5.0-6.5 

Beef 

1 

1.7 

Turnips 

.     1 

6 

Cheese    . 

1 

0.7 

Onions 

.    1 

6 

Meat 

1 

0.5-1.5 

Oatmeal 

.     1 

5.5 

Veal       . 

1 

0.1 

Cocoa 

.     1 

5 

White  of  egg  . 

1 

0 

Nutrition.  In  the  process  of  nutrition  five  phases  may  be  dis- 
tinguished, viz. :  Digestion,  absorption,  assimilation,  destructive  meta- 
morphosis, and  elimination  of  waste  products. 

Digestion  is  the  process  of  converting  food  material  into  dialyzable 
compounds,  or  into  other  forms  of  matter  capable  of  absorption. 
Absorption  is  the  mechanical  process  of  transferring  the  digested 
materials  from  the  alimentary  canal  into  the  circulation.  Assimila- 
tion includes  the  changes  taking  place  after  they  are  absorbed  until 
they  have  become  a  part  of  living  cells.  Destructive  metamorphosis 
includes  those  changes  which  take  place  chiefly  in  consequence  of 
oxidation,  the  oxygen  being  supplied  during  the  process  of  respira- 
tion. Elimination  of  waste  products  is  the  discharge  of  that  material 
which  is  no  longer  needed  in  the  system. 

Digestion.  It  has  been  stated  before  that  foods  are  divided  into 
two  classes,  inorganic  and  organic,  and  that  the  latter  are  subdivided 


CHEMICAL  CHANGES  IN  PLANTS  AND  ANIMALS.  425 

into  albuminoids,  carbohydrates,  and  fats.  As  a  rule,  the  inorganic 
foods  are  taken  into  the  body  without  chemical  change.  Before  the 
organic  foods  can  be  absorbed,  they  have  to  undergo  digestion.  This 
is  the  process  by  which  organic  compounds,  capable  of  acting  as  foods, 
are  so  altered  that  they  may  be  absorbed. 

The  first  part  of  the  process  of  digestion  is  accomplished  in  the 
mouth  and  consists  in  the  breaking  up  of  the  food  by  the  teeth  and 
mixing  it  with  saliva,  the  process  being  known  as  mastication.  In 
addition,  the  saliva,  to  a  limited  extent,  converts  starch  into  maltose. 
This  action  of  the  saliva  is  due  to  its  ferment  ptyalin.  Other  func- 
tions of  the  saliva  are  to  keep  the  mucous  membrane  of  the  mouth 
moist  and  to  lubricate  the  food  bolus. 

After  being  masticated,  the  food  is  passed  into  the  stomach,  where 
it  comes  in  contact  with  the  gastric  juice.  The  active  principles  of 
the  gastric  juice  are  free  hydrochloric  acid,  which  is  present  in  from 
0.1  to  0.2  per  cent.,  and  the  ferments  pepsin  and  rennet.  The  pro- 
teids  are  the  only  compounds  aifected  by  the  gastric  juice.  The  free 
acid  first  converts  them  into  syntonin,  which  is  soluble  in  dilute  acids, 
but  is  insoluble  in  water  or  solutions  of  neutral  salts.  The  pepsin 
causes  syntonin  to  take  up  water,  converting  it  into  albumoses  and 
peptones,  which  latter,  as  stated  in  chapter  51,  are  dialyzable,  and 
soluble  in  water,  dilute  acids,  dilute  alkalies,,  and  neutral  solutions. 
Rennet  ferment  has  the  power  of  coagulating  milk  in  neutral  solu- 
tion— that  is,  of  precipitating  the  casein.  Starch  cells  and  fat 
globules  are  set  free  by  the  gastric  juice  acting  upon  their  albu- 
minous envelopes. 

After  the  food  has  been  acted  upon  by  the  gastric  juice  it  forms  a 
very  turbid  mixture,  chyme,  which,  by  the  contraction  of  the  stomach, 
is  forced  through  the  pyloric  orifice  into  the  small  intestine.  Here 
it  soon  comes  in  contact  with  the  bile  and  pancreatic  juice. 

The  functions  of  the  bile  as  a  digestive  fluid  are  :  to  assist  in  the 
em  unification  of  neutral  fats ;  to  promote  the  absorption  of  fats ;  by 
its  diastatic  ferment  to  convert  starch  and  glycogen  into  sugar ;  to 
stimulate  intestinal  peristalsis ;  to  assist  in  the  evacuation  of  the 
feces,  to  which  it  furnishes  the  coloring  matter ;  and,  finally,  to  act 
as  an  intestinal  antiseptic. 

Pancreatic  juice  is  alkaline  in  reaction  and  contains  most  likely 
four  ferments,  trypsin,  steapsin,  amylopsiu,  and  one  unnamed.  Much 
the  larger  portion  of  fats  are  simply  emulsified  by  the  pancreatic 
juice.  Under  the  influence  of  steapsin  a  small  portion  is  broken  up 
into  fatty  acids  and  glycerin.  For  example  : 


426  PHYSIOLOGICAL  CHEMISTRY. 

C3H6.(C18H350)303    +    3H20    =    3C18H3602    +    C3H5(OH)3. 
Stearin.  Water.  Stearic  acid.  Glycerin. 

A  portion  of  the  alkali  present  then  unites  with  the  fatty  acid  to 
form  a  dialyzable  soap. 

Amylopsin  acts  upon  starches,  converting  them  into  maltose.  The 
change  is  one  of  hydration  : 

2C6H1006    +    H20    =    C12H22On. 
Starch.  Maltose. 

Any  albuminoids  that  may  have  escaped  the  action  of  the  gastric 
juice  are  converted  into  peptones  by  trypsin.  In  this  process,  which 
is  apparently  one  of  hydration,  the  intermediate  compound  syntonin 
is  not  formed.  The  fourth,  assumed  and  unnamed  ferment  of  pan- 
creatic juice,  has  the  property  of  coagulating  casein. 

In  addition  to  the  above  considered  digestive  fluids,  there  are  the 
intestinal  juices.  They  are,  however,  so  small  in  quantity  and  so 
difficult  of  investigation  that  little  is  known  of  their  action.  They 
probably  have  properties  similar  to  the  pancreatic  juice,  though 
weaker  than  that  secretion.  By  the  combined  action  of  the  various 
digestive  fluids,  the  chyme  is  gradually  converted  into  chyle.  It  is  a 
milky-white,  or  occasionally  a  yellowish  fluid,  having  an  alkaline 
reaction,  a  faint  smell,  a  saltish  taste,  and  a  specific  gravity  varying 
from  1.007  to  1.022.  It  is  this  chyle  which  is  absorbed  by  the  intes- 
tinal villi,  and  forms  the  material  from  which  the  blood  is  constantly 
renewed. 

Absorption.  Assimilation.  All  forms  of  food  that  are  dialyzable 
when  taken  into  the  stomach,  or  that  are  there  converted  into  dia- 
lyzable compounds,  are,  for  the  most  part,  taken  directly  into  the 
radicles  of  the  portal  vein  by  osmose.  The  products  of  intestinal 
digestion  make  their  way  partly  into  the  bloodvessels  and  partly  into 
the  lacteals.  It  has  been  shown  that  the  larger  portion  of  fats  which 
are  not  dialyzable  get  into  the  lacteals  as  fats,  and  not  as  dialyzable 
soaps.  At  present  we  do  not  understand  the  process  by  which  this 
absorption  of  emulsified  fats  takes  place. 

All  material  absorbed  by  the  lacteals  is  carried  by  the  thoracic  duct 
and  poured  into  the  left  subclavian  vein.  All  material  taken  up  by 
the  portal  vein  is  first  carried  to  the  liver.  In  the  liver  the  maltose 
undergoes  dehydration,  being  thereby  converted  into  an  insoluble 
compound,  isomeric  with  starch,  and  termed  glycogen.  This  glycogen 
is  stored  up  in  the  liver,  and  when  wanted  in  the  system  is  recon- 
verted into  soluble  maltose. 


CHEMICAL  CHANGES  IN  PLANTS  AND  ANIMALS.  427 

Respiration.  The  most  important  changes  in  respired  air  are  the 
changes  in  the  quantities  of  oxygen  and  carbon  dioxide.  Pure  air, 
after  being  dried,  contains,  by  volume,  of  oxygen  20.8  per  cent.,  of 
nitrogen  79.2  per  cent.,  and  a  quantity  of  carbon  dioxide  (0.04  per 
cent.)  so  small  that  it  need  not  be  considered.  When  100  volumes  of 
air  have  been  breathed  once,  it  gains  a  little  more  than  four  parts  of 
carbon  dioxide  and  loses  a  little  more  than  five  parts  of  oxygen ;  so 
that  the  composition  of  100  volumes  of  inspired  air,  when  expired,  is, 
after  being  dried,  oxygen  15.4  parts,  nitrogen  79.2  parts,  and  carbon 
dioxide  4.3  parts  by  volume. 

Much  the  greater  portion  of  the  oxygen  lost  from  respired  air 
enters  into  combination  with  the  haemoglobin ;  a  small  portion  is 
absorbed  by  the  blood-serum.  The  immediate  source  of  the  carbon 
dioxide  is  the  blood,  in  which  it  exists  partly  in  simple  solution  and 
partly  in  a  loose  combination  with  some  unknown  body. 

The  blood  is  the  common  carrier  of  the  body  :  from  the  alimentary 
canal  it  receives  ultimately  all  the  food  material ;  from  the  lungs  it 
receives  oxygen  ;  these  it  carries  to  the  tissues  for  their  sustenance ; 
from  the  tissues  it  receives  the  products  of  destructive  metamorphosis, 
and  carries  them  to  their  proper  organs  of  elimination. 

The  bright-red  color  of  the  arterial  blood  is  due  to  oxyhsemoglobin. 
A  large  portion  of  this  oxygen  absorbed  by  the  haemoglobin  is  given 
up  to  the  tissues  as  the  blood  passes  through  the  capillaries,  and  we 
have  then  the  reduced  haemoglobin  to  which  is  due  the  dark  color  of 
the  venous  blood. 

In  some  way,  not  understood,  the  blood-plasma  takes  up  the  carbon 
dioxide  from  the  tissues  and  carries  it  to  the  lung.  It  has  been  shown 
that  the  dark  color  of  the  venous  blood  is  not  due  to  the  presence  of 
carbon  dioxide,  but  to  a  decrease  of  the  oxygen. 

In  suspension  in  the  plasma  are  found  the  food  materials  on  their 
way  to  different  portions  of  the  body.  A  small  percentage  of  pep- 
tones is  found,  but  the  quantity  is  so  insignificant  in  proportion  to 
the  total  amount  absorbed,  that  it  is  extremely  probable  that  they  are 
converted  into  the  more  common  forms  of  albumin. 

"Waste  products  of  animal  life.  The  changes  which  the  food 
suffers  after  having  been  absorbed  by  the  animal  system  are  ex- 
tremely complicated,  and  far  from  being  thoroughly  understood. 
Numerous  products  and  organs  are  formed  and  nourished  from 
and  by  the  blood  ;  among  them  muscular,  nerve,  and  brain  sub- 
stance, excretions  and  secretions,  such  as  milk,  saliva,  bile,  gastric 


428  PHYSIOLOGICAL  CHEMISTRY. 

and  pancreatic  juice,  etc.,  together  with  bones,  teeth,  hair,  and  many 
others. 

Most  of  these  substances  (some  excretions,  such  as  milk  and  others, 
excepted)  suffer  a  constant  oxidation  in  the  system,  and  are  finally 
eliminated  as  waste  products  ;  in  regard  to  the  intermediate  com- 
pounds formed  in  the  tissues  we  know  little,  but  it  is  highly  probable 
that  the  reduction  of  the  complicated  food  material  to  the  simple 
forms  of  the  waste  products  is  very  gradual.  There  are  three  chan- 
nels through  which  the  waste  products  are  given  off;  they  are  the 
lungs,  the  skin,  and  the  kidneys.  By  the  lungs  are  eliminated 
chiefly  carbon  dioxide  and  some  water,  by  the  kidneys  urine  (which 
is  a  weak  aqueous  solution  of  urea,  uric  acid,  urates,  phosphates, 
chlorides,  and  sulphates  of  calcium,  magnesium,  sodium,  potassium, 
etc.),  and  by  the  skin  are  constantly  eliminated  carbon  dioxide  and 
water,  and  during  the  process  of  sweating  also  more  or  less  of  the 
constituents  of  urine. 

Chemical  changes  after  death.  After  the  death  of  either  a 
plant  or  an  animal,  a  chemical  decomposition  commences  which  finally 
results  in  the  formation  of  those  inorganic  compounds  from  which 
the  plant  originally  derived  its  food,  viz.,  carbon  dioxide,  water, 
ammonia,  sulphates,  phosphates,  etc.  This  decomposition  of  a  dead 
body  is  generally  a  simultaneous  fermentation  or  putrefaction,  aided 
by  decay  or  slow  combustion. 

There  are  numerous  intermediate  products  formed,  which  differ 
according  to  the  nature  of  the  decomposing  substance,  or  according 
to  the  conditions  (degree  of  temperature,  amount  of  moisture  and  air 
present,  etc.)  under  which  the  decomposition  takes  place. 

During  the  decomposition  of  dead  vegetable  matter  (especially  of 
moist  wood)  the  intermediate  products  are  frequently  called  humus, 
which  substance  (or  better,  mixture  of  substances)  forms  the  chief 
part  of  the  organic  matter  in  the  soil. 

During  the  decomposition  of  dead  animals,  the  sulphur  is  first 
eliminated  as  hydrogen  sulphide,  and  a  number  of  other  intermediate 
products  have  been  shown  to  be  formed  ;  among  them  certain  organic 

QUESTIONS. — 511.  What  is  the  difference  between  vegetable  and  animal  life 
from  a  chemieaLpoint  of  view  ?  512.  Mention  the  chief  substances  serving  as 
plant  food.  513.  Explain  the  formation  of  organic  substances  in  the  plant. 

514.  What  elements  enter  into  the  animal  system  as  necessary  constituents  ? 

515.  The  members  of  which  three  groups  of  organic  substances  are  chiefly  used 
as  food  by  animals  ?    516.  Give  a  full  explanation  of  respiration.    517.  Explain 


ANIMAL  FLUIDS  AND  TISSUES.  429 

bases  called  ptomaines  or  cadaveric  alkaloids,  substances  which  have 
been  spoken  of  in  Chapter  50.  The  decomposition  of  organic  matter 
may  be  prevented  under  conditions  which  have  been  mentioned  here- 
tofore in  connection  with  putrefaction. 

53.  ANIMAL  FLUIDS  AND  TISSUES. 

Constituents  of  the  animal  body.  The  animal  body  consists 
mainly  of  three  kinds  of  matter,  viz.,  water,  organic  and  inorganic 
matter.  It  contains  of  water  about  70  per  cent.,  of  organic  matter 
25  per  cent.,  and  of  inorganic  matter  about  5  per  cent.  The  water 
may  be  determined  by  drying  a  weighed  quantity  in  an  air-bath  at  a 
temperature  of  100°  to  105°  C.  (212°  to  221°  F.);  the  organic  matter 
is  estimated  by  burning  the  dried  substance,  and  the  inorganic  matter 
(ash)  by  weighing  the  residue.  Some  of  the  elements  which  are  left 
in  the  inorganic  residue  have,  however,  been  actually  constituents  of 
organic  compounds ;  iron,  for  instance,  which  is  left  in  the  ash,  has 
been  chiefly  a  constituent  of  haemoglobin  ;  sulphur,  left  as  a  sulphate, 
may  have  been  a  constituent  of  albumin,  etc. 

The  relative  quantities  of  the  three  constituents  in  some  of  the 
animal  fluids  and  tissues  is  shown  in  the  following  table  : 

Organic  and       Inorganic  resi- 
volatiie  matter.         due  (ash). 


Saliva    .... 

.     99.50 

0.32 

0.18 

Gastric  juice 
Pancreatic  juice    . 
Bile       .... 
Chyle    .... 

.     9943 
.    90.97 
.    85.92 
91.80 

0.33 

8.18 
13.30 
7.40 

0.24 
0.85 
0.781 
0.80 

Lymph 
Pus       .... 

.    9180 
.    87.00 

7-40 
12.20 

0.80 
0.80 

Cows'  milk    . 

.    87.00 

12.25 

0.75 

Human  milk 

.    86.80 

12.85 

0.35 

Blood    .... 

.    79.50 

19.70 

0.80 

Blood  corpuscles  . 
Blood  serum 

.    54.60 
.    90.50 

44.68 
8.68 

0.72 

0.82 

Urine    .... 

.    95.70 

3.00 

1.30 

Bone  (varies  widely)     . 
Dentine 

.     22.00 
.     10.00 

26.00 
25.00 

52.00 
65.00 

Enamel 

.       0.40 

3.60 

96.00 

the  chemical  changes  which  food  suffers  during  digestion.  518.  Mention  the 
principal  fluids  which  are  secreted  by  various  organs  of  the  animal  body  in 
order  to  facilitate  or  cause  digestion.  519.  What  are  the  waste  products  of 
animal  life,  and  through  which  channels  are  they  eliminated  ?  520.  What  is 
the  final  result  of  the  decomposition  of  dead  plants  or  animals  ? 

i  The  metals  in  combination  with  the  biliary  acids  not  included. 


430  PHYSIOLOGICAL  CHEMISTRY. 

The  complex  nature  of  the  various  organic  matters  has  been  referred 
to  in  the  preceding  chapter,  and  will  be  more  fully  considered  below; 
but  it  may  be  mentioned  here,  that  some  of  these  organic  substances 
(or  groups  of  substances)  may  be  separated  by  a  successive  treatment 
of  the  animal  matter  with  various  solvents.  Thus,  by  treating  with 
ether  or  carbon  disulphide,  all  fats  may  be  extracted  ;  by  then  treat- 
ing with  alcohol  and  water  successively  other  substances  (generally 
termed  extractive  matter  or  extractives)  are  dissolved,  which  may  be 
obtained  by  evaporating  the  solution. 

Among  the  extractives  are  found  kreatin  and  kreatinin,  urea,  uric 
acid,  organic  salts,  etc.  After  the  fatty  matter  and  the  extractives 
have  been  removed  there  remains  an  elastic  and  somewhat  horny 
mass,  which  consists  chiefly  of  proteids  (albumin,  fibrin,  globulin,  etc.). 

The  complete  separation  of  all  substances  is  extremely  difficult  on 
account  of  the  great  similarity  in  properties  of  many  of  these  sub- 
stances, and  the  rapid  changes  which  they  suffer  when  acted  upon  by 
solvents  or  chemical  agents. 

As  the  nature  or  composition  of  many  of  the  inorganic  salts  present 
in  the  animal  tissues  is  changed  during  the  burning  off  of  the  organic 
matter,  it  is  necessary  to  determine  them  either  in  the  aqueous  solu- 
tion (extract)  or  by  subjecting  the  animal  matter  to  dialysis,  by  which 
process  they  may  be  more  or  less  completely  separated  from  the  organic 
matter,  which  is  left  in  the  dialyzer,  whilst  the  salts  pass  through  the 
membrane. 

Experiment  63.  Cut  a  mouse  (or  some  other  small  animal)  into  fragments 
weigh  and  place  them  in  a  weighed  dish ;  expel  all  water  by  heating  the  dish 
first  over  a  water-bath,  and  then  in  an  air-bath  at  a  temperature  of  about  110° 
C.  (230°  F.)  until  there  is  no  longer  any  loss  in  weight ;  this  loss  is  the  amount 
of  water  present  in  the  animal.  Disintegrate  the  dry  pieces  further  by  grind- 
ing in  a  mortar  and  cutting  with  a  pair  of  scissors,  mix  well  and  ignite  a  few 
grammes  in  a  platinum  crucible  until  all  organic  matter  is  burned  off  and  a 
white  or  nearly  white  residue  of  inorganic  matter  is  left.  (Complete  combus- 
tion is  facilitated  by  cooling  and  heating  alternately  several  times,  since  the 
animal  charcoal,  left  after  the  first  ignition,  readily  absorbs  atmospheric  oxy- 
gen, which  aids  in  combustion  when  again  heated.)  From  the  results  obtained 
by  the  ignition  of  the  portion  of  dry  animal  matter  calculate  the  organic  and 
inorganic  matter  of  the  animal  operated  on. 

Digest  the  inorganic  residue  with  water,  filter  and  test  in  the  filtrate  for 
chlorides  by  silver  nitrate.  Dissolve  the  residue  upon  the  filter  in  dilute  hydro- 
chloric acid  and  test  portions  of  this  solution  for  phosphoric  acid  by  means  of 
ammonium  molybdate ;  for  iron  by  potassium  ferrocyanide  ;  for  sulphuric  acid 
by  barium  chloride,  and  for  calcium  by  adding  an  excess  of  sodium  acetate 
and  then  ammonium  oxalate. 


ANIMAL  FLUIDS  AND  TISSUES.  431 

Weigh  a  few  grammes  of  the  dried  animal  matter  and  digest  it  in  a  stop- 
pered flask  with  about  10  parts  of  ether  for  an  hour ;  filter,  and  repeat  the 
operation  once  or  twice ;  allow  the  ether  to  evaporate  in  a  small  dish,  previ- 
ously weighed ;  the  residue  left  consists  chiefly  of  fats,  which  may  be  recognized 
by  their  physical  properties. 

Digest  the  animal  matter  left  from  previous  treatment  twice  with  hot  alcohol 
and  twice  with  boiling  water ;  evaporate  the  alcoholic  and  aqueous  solutions 
separately ;  they  contain  the  so-called  extractives  and  soluble  salts. 

Dry  the  exhausted  animal  matter  completely  as  before  and  weigh  it ;  it  con- 
sists chiefly  of  insoluble  salts  and  albuminous  substances.  Ignite  and  burn 
as  stated  above.  The  loss  represents  mainly  albuminoids.  Notice  the  differ- 
ence between  the  percentage  of  inorganic  matter  left  now  and  in  the  deter- 
mination made  before ;  this  difference  represents  the  soluble  inorganic  com- 
pounds. 

Blood.  Two  kinds  of  blood  are  distinguished,  the  arterial  or  oxi- 
dized and  the  venous  or  deoxidized  blood.  Arterial  blood  as  it  is 
present  in  the  system,  or  immediately  after  it  has  been  drawn  from 
the  body,  is  a  red  liquid  of  an  alkaline  reaction  and  a  specific  gravity 
of  about  1055.  Upon  examination  under  the  microscope,  blood  is 
seen  to  consist  of  a  colorless  fluid,  called  plasma  or  serum,  in  which 
float  small  globules  or  corpuscles  which  make  up  about  40  per  cent, 
of  the  whole  volume  of  blood.  These  corpuscles  are  of  three  varie- 
ties, viz. :  red  and  white  corpuscles,  and  blood  plates.  The  red  cor- 
puscles, which  give  to  the  blood  its  red  color,  are  biconcave  discs, 
about  33*00  of  an  inch  in  diameter;  the  white  corpuscles  are  simple 
cells,  and  somewhat  larger  than  the  red  corpuscles ;  they  are  present 
in  the  proportion  of  about  1  to  350  of  red.  More  recently  have  been 
discovered  "blood  plates,"  pale,  colorless,  oval,  round  or  lenticular 
discs  which  vary  in  size. 

The  composition  of  normal  human  blood  is  about  as  follows : 

Water .        .        .  79.50  per  cent. 

Serum-albumin 7.34  " 

Fibrin 0.21  " 

Haemoglobin 11.64  " 

Fatty  matters 0.18  " 

Extractives 0.32  " 

Ash 0.81 

AYet  red  blood-corpuscles  contain  of  water  54.63  per  cent.,  haemo- 
globin 41.1  per  cent.,  other  proteids  3.9  per  cent.,  fats  (chiefly  chole- 
sterin  and  lecithin)  0.37  per  cent.  The  quantity  of  water  in  corpus- 
cles varies  widely,  and  most  likely  ranges  in  healthy  blood  from  76 
to  80  per  cent.  Dried  corpuscles  contain  of  haemoglobin  about  90 
per  cent. 


432  PHYSIOLOGICAL  CHEMISTRY. 

The  white  blood-corpuscle  consists  of  a  thin  envelope  filled  with  an 
albuminoid  (or  a  mixture  of  them)  called  protoplasm. 

The  blood-plasma  is  a  colorless  liquid  of  the  average  composition 
as  follows : 

Per  cent. 

Water 90.20 

Albumin •  5.30 

Fibrinoplastin 2.20 

Fibrinogen 0.30 

Fatty  matters 0.25 

Crystallizable  nitrogenous  matter 0.40 

Other  organic  ingredients 0.50 

Mineral  salts          .        . 0.85 

The  alkaline  reaction  of  blood  is  due  to  the  presence  of  acid  sodium 
carbonate,  NaHCO3,  and  sodium  phosphate,  Na2HPO4,  both  of  which 
have  a  weak  alkaline  reaction.  Besides  these  alkaline  salts,  blood 
also  contains  others,  among  them  chiefly  sodium  chloride,  and  also  the 
chlorides,  phosphates,  and  sulphates  of  calcium,  magnesium,  sodium, 
potassium,  etc. 

When  blood  leaves  the  body  and  is  allowed  to  stand  a  while  (or, 
quicker,  on  shaking  or  agitating  it  violently)  it  separates  into  a  semi- 
solid  mass  termed  clot,  and  a  pale-yellow  liquid  termed  serum,  which 
latter,  however,  also  solidifies  after  a  time  in  consequence  of  the  coag- 
ulation of  the  serum-albumin.  Clot  consists  of  fibrin,  holding  in  its 
meshes  the  blood  corpuscles ;  the  latter  may  be  removed  by  washing 
the  clot  in  a  stream  of  water.  Another  method  for  obtaining  the 
corpuscles  is  to  dilute  mammalian  blood  with  10  volumes  of  a  2  per 
cent,  sodium  chloride  solution,  which  prevents  coagulation,  but  allows 
the  corpuscles  to  settle  at  the  bottom  of  the  fluid. 

Fibrin  is  a  proteid,  which  exists  not  as  such  in  the  blood,  but 
forms  whenever  the  latter  is  taken  from  the  body  (or  under  some  cir- 
cumstances when  within  the  living  body).  It  is  now  assumed,  that 
for  the  formation  of  fibrin  four  factors  are  necessary,  viz.,  fibrino- 
plastin,  fibrinogen,  fibrin  ferment,  and  a  small  portion  of  neutral 
salts.  The  origin  of  the  fibrin  ferment  is  not  positively  known,  but 
it  is  supposed  to  come  from  the  edges  of  the  wounded  bloodvessels. 
The  other  factors  are  all  present  in  the  blood.  How  these  substances 
by  their  interaction  produce  fibrin  is  not  known ;  fibrinogen  is  the 
only  one  of  which  the  total  quantity  is  used.  There  is  always  an 
excess  of  fibrino-plastin.  While  the  presence  of  fibrin  ferment  and 
neutral  salts  is  necessary,  their  quantities  do  not  seem  to  be  diminished. 
The  blood  corpuscles  take  no  active  part  in  the  formation  of  the  clot, 
but  are  simply  entangled  in  its  meshes. 


ANIMAL  FLUIDS  AND  TISSUES.  433 

Hcemoglobin  is  the  chief  constituent  of  the  red  corpuscles,  and  the 
substance  which  carries  oxygen  to  the  various  tissues,  as  described  in 
connection  with  the  consideration  of  the  process  of  respiration  in  the 
previous  chapter. 

Experiment  64.  Pour  some  freshly  drawn  venous  blood  into  four  volumes  of 
a  saturated  solution  of  sodium  sulphate  contained  in  a  vessel  which  stands  in 
ice ;  mix  and  set  aside  for  several  hours ;  no  coagulation  occurs  and  the  cor- 
puscles settle  to  the  bottom  of  the  vessel.  Pour  off  the  supernatant  liquid, 
collect  the  sediment  on  a  filter,  and  wash  it  first  with  cold  solution  of  sodium 
sulphate  and  then  with  water. 

Prepare  haemoglobin  from  these  corpuscles  as  follows :  agitate  the  collected 
mass  violently  with  small  quantities  of  ether  until  the  corpuscles  are  nearly 
dissolved ;  allow  the  liquid  to  settle,  filter,  render  the  filtrate  slightly  acid  with 
acetic  acid,  and  add  alcohol  as  long  as  the  precipitate  first  formed  continues  to 
dissolve ;  cool  the  red  solution  to  0°  C.  (32°  F.)  for  several  hours,  when  crystals 
of  haemoglobin  will  form ;  collect  these  on  a  filter  and  wash  with  an  ice-cold 
mixture  of  alcohol  and  water. 

Examination  of  blood-stains.  Blood-stains  may  be  recognized, 
after  having  been  washed  off  with  as  little  water  as  possible,  by  the 
following  methods : 

1.  Examine  the  reddish  fluid  under  the  microscope  for  blood  cor- 
puscles. 

2.  Evaporate  a  drop  of  the  fluid  on  a  microscope  slide  with  a 
minute  fragment  of  sodium  chloride,  cover  with  a  cover-glass,  allow 
a  drop  of  glacial  acetic  acid  to  enter  from  the  side  and  warm  gently; 
abundant  crops  of  hsemin  crystals  are  seen  under  the  microscope 
after  cooling. 

3.  Add  a  drop  of  the  fluid  to  some  freshly  prepared  tincture  of 
guaiacum  in  a  test-tube  and  float  on  the  surface  of  an  ethereal  solu- 
tion of  hydrogen  dioxide;  a  blue  ring  forms  at  the  junction  of  the 
ethereal  solution  and  the  guaiacum.     (Blood  is,  however,  not  the  only 
substance  showing  this  reaction. 

4.  The  spectroscope  shows  bands  characteristic  of  haemoglobin. 

Chyle  is  a  white,  creamy  liquid,  of  a  strongly  alkaline  reaction, 
having  in  common  with  blood  the  property  of  coagulating  (upon 
leaving  the  organism)  into  white  fibrin  and  turbid  serum.  The  com- 
position of  chyle  differs  according  to  the  state  of  digestion ;  it  contains : 

During  full  digestion.         During  fasting. 

Water 91.8  per  cent.  96.80  per  cent. 

Fibrin 0.2        "  0.09 

Proteids 3.5         "  2.30        " 

Fats 3.3  0.04 

Extractives        .        .        .        .0.4        "  0.28        « 

Salts 0.8  0.49        " 

28 


434  PHYSIOLOGICAL  CHEMISTRY. 

Lymph  is  a  clear,  colorless,  or  slightly  yellow  liquid  of  a  faint 
alkaline  reaction ;  in  composition  it  closely  resembles  chyle,  but 
differs  from  it  in  containing  smaller  quantities  of  fibrin  and  fatty 
matters. 

Saliva  is  secreted  by  several  glands  situated  in  the  mouth,  and 
represents  in  its  mixed  condition  a  viscid,  generally  slightly  alkaline, 
tasteless,  inodorous  liquid  of  a  specific  gravity  of  1.002  to  1.008.  It 
contains  of 

Water 99U9  per  cent. 

Ptyalin 0.12        " 

Epithelium  and  mucin 0.13         " 

Fatty  matters 0.11         " 

Salts 0.15 

Ptyalin,  the  active  principle  of  saliva,  is  a  ferment  which  has  the 
power  of  converting  starch  into  maltose  and  small  quantities  of 
dextrose.  Intermediary  between  the  starch  and  sugar  are  two 
products  known  as  erythrodextrin  and  achroodextrin.  Starch  is  recog- 
nized by  a  deep  blue  color  produced  by  a  solution  of  iodine  and 
potassium  iodide  in  water.  Erythrodextrin  gives  a  mahogany 
brown  or  violet  color,  and  achroodextrin,  maltose  or  dextrose  do  not 
color  the  iodine  solution  at  all.  The  composition  of  ptyalin  is 
doubtful.  Among  the  various  salts  of  saliva  is  found  potassium 
sulphocyanate,  as  may  be  shown  by  the  addition  of  a  drop  of  ferric 
chloride  solution,  which  produces  a  deep  red  color,  disappearing  on 
the  addition  of  mercuric  chloride  (difference  from  meconic  acid). 

Experiment  65.  To  a  few  c.c.  of  thin  starch  paste  add  an  equal  volume  of 
saliva,  mix  well  and  digest  at  a  temperature  of  35°-40°  C.  (95°-104°  F.)  for 
about  half  an  hour.  Examine  the  liquid  for  sugar  by  Fehling's  solution. 

Gastric  juice  is  a  liquid  secreted  by  the  follicles  of  the  stomach. 
It  can  be  obtained,  in  a  fairly  normal  condition,  either  from  animals 
(dogs)  or  from  man,  by  the  aid  either  of  gastric  fistulse,  or'  of  the 
stomach-pump.  It  is  a  thin,  nearly  colorless  liquid,  having  a  some- 
what sour  taste,  an  acid  reaction,  and  a  specific  gravity  varying  from 
1.004  to  1.010.  The  total  solids  are  generally  less  than  1  per  cent., 
nearly  one-half  being  inorganic  salts,  chiefly  the  chlorides  and  phos- 
phates of  alkali  and  alkaline  earth  metals.  The  organic  matter 
present,  and  amounting  to  about  0.3  per  cent.,  is  chiefly  pepsin  and  a 
little  mucin. 

Organic  acids,  chiefly  lactic  and  butyric,  are  frequently  found  in 


ANIMAL  FLUIDS  AND  TISSUES.  435 

the  stomach,  but  these  are  not  secreted  in  the  gastric  juice  itself,-  but 
are  produced  by  some  fermentative  action  from  the  food  after  it  has 
entered  the  stomach.  The  acidity  of  gastric  juice  itself  is  due  to  free 
hydrochloric  acid,  present  in  quantities  varying  from  0.1  to  0.3,  or 
even  0.4  per  cent. 

The  nature  of  the  decomposition  resulting  in  the  liberation  of  free  hydro- 
chloric acid  is  not  known,  but  it  may  possibly  be  formed  by  the  action  of 
sodium  phosphate  on  calcium  chloride  : 

2(Na2HPO4)     -f     3CaCl2    =   =    Ca3(PO4)2    +     4NaCl    +     2HC1. 

Sodium  Calcium  Calcium  Sodium        Hydrochloric 

phosphate.  chloride.  phosphate.  chloride.  acid. 

According  to  others,  the  hydrochloric  acid  is  liberated  by  the  action  of  acid 
sodium  carbonate  on  sodium  chloride  : 


NaHC03     +     Nad     =    Na^COg     +     HC1. 
Sodium  acid          Sodium  Sodium        Hydrochloric 

carbonate.  chloride.         carbonate.  acid. 

The  above  formulas  show  the  reverse  action  of  that  which  these  substances 
exert  upon  each  other  under  common  conditions,  but  it  must  be  remembered 
that  the  living  cell  is  capable  of  decomposing  matter  generally  in  a  manner 
different  from  that  which  it  suffers  ordinarily. 

The  average  composition  of  pure  gastric  juice  may  be  approxi- 
mately stated  thus  : 

Water        .........  99.26  per  cent. 

Pepsin  and  other  organic  matter       ....  0.30        " 

Kennet       .........         ?  " 

Free  hydrochloric  acid      ......  0.22         " 

Alkali  chlorides         .......  0.20        " 

Phosphates  of  calcium,  magnesium,  and  iron    .        .  0.02        " 

Pepsin,  besides  hydrochloric  acid,  the  most  important  constituent 
of  gastric  juice,  has  been  spoken  of  heretofore  ;  it  has,  in  the  pres- 
ence of  free  hydrochloric  acid,  the  power  of  converting  proteids  into 
albumoses,  and  finally  into  peptones.  Pepsin  is  not  secreted  by  the 
gastric  tubules  as  such,  but  in  a  preliminary  stage  or  pro-enzyme  (pep- 
sinogen),  and  is  changed  by  the  hydrochloric  acid  into  pepsin. 

Another  ferment,  known  as  rennet,  is  found  in  the  gastric  secretion. 
Like  pepsin,  it  is  secreted  in  a  preliminary  stage  or  pro-enzyme  (rennet 
zymogen).  Rennet  has  the  power  of  coagulating  milk  in  neutral 
solutions,  that  is,  of  precipitating  the  casein. 

Experiment  66.  Open  the  stomach  of  a  pig,  sheep  j  or  calf,  recently  killed 
while  fasting  ;  wash  it  rapidly  in  cold  water,  spread  it  out  and  scrape  off  the 
mucous  surface  ;  digest  it  under  frequent  stirring  with  about  ten  parts  of  water 
for  six  hours,  and  filter.  The  solution  contains  pepsin—  which  verity  by  its 
dissolving  action  on  coagulated  albumin. 


436  PHYSIOLOGICAL  CHEMISTRY. 

The  solution  may  also  be  evaporated  to  dryness  with  or  without  sugar  at  a 
temperature  not  exceeding  40°  C.  (104°  F.),  and  the  dry  pepsin  tested  by  the 
directions  given  in  Experiment  62. 

Clinical  examination  of  gastric  juice.  The  chemical  examina- 
tion of  gastric  juice,  or  of  contents  of  stomach,  is  now  considered  of 
great  importance  in  the  diagnosis  of  diseases  of  the  stomach.  The 
juice  for  examination  is  obtained  as  follows  :  On  an  empty  stomach, 
the  patient  partakes  of  a  test-meal,  consisting  usually  of  bread  and 
water,  and  an  hour  after  or  later  (depending  upon  the  form  of  meal 
administered),  the  contents  of  the  meal  are  withdrawn  by  means  of  a 
stomach-tube.  The  liquid  is  filtered  and  used  for  further  examina- 
tions. These  examinations  consist  of  the  following  determinations : 
a.  Keaction ;  b.  presence  of  free  acids ;  c.  presence  of  free  hydro- 
chloric acid ;  d.  presence  of  lactic  and  other  organic  acids ;  e .  total 
acidity ;  f.  estimation  of  free  hydrochloric  acid ;  g.  presence  of  pepsin 
and  pepsinogen  ;  h.  presence  of  rennet  ferment  and  rennet  zymogen ; 
i.  detection  of  proteids ;  j.  detection  of  carbohydrates. 

a.  Reaction.     This  should  be,  and  in  all  normal  juices  is,  distinctly 
acid  to  litmus  paper. 

b.  Free  acids.     The  presence  of  free  acids  is  detected  by  congo- 
paper.     This  paper  is  prepared  by  soaking  unsized  paper  in  a  1  per 
cent,  aqueous  solution  of  congo-red,  and  drying.     If  a  drop  of  juice 
is  placed  upon  the  paper,  the  presence  of  free  acids  is  indicated  by 
the  change  of  color  from  red  to  blue ;  if  the  blue  color  is  intense, 
free  hydrochloric  acid  is  present.     (Acid  salts,  such  as  acid  phos- 
phates, do  not  act  on  congo-red.) 

c.  Free  hydrochloric  acid.     There  are  a  number  of  reagents  for 
the  detection  of  free  hydrochloric   acid.      The  more   important  of 
these  are :   methyl-violet,  tropseolin  0  0,  phloroglucin-vanillin,  and 
resorcin. 

Methyl-violet.  If  a  concentrated  aqueous  solution  of  methyl-violet 
is  prepared  and  added  to  gastric  juice  containing  free  hydrochloric 
acid,  a  change  from  violet  to  blue  is  at  once  noted. 

Tropceolin  0  0.  Dissolved  in  alcohol  the  brownish-yellow  solution 
of  tropseolin  0  0  (diphenylamine-orange)  is  changed  to  a  brown-red 
or  deep-red  color  upon  the  addition  of  juice  containing  free  hydro- 
chloric acid.  The  same  reaction  may  be  made  with  filter-paper, 
soaked  for  some  time  in  an  alcoholic  solution  of  the  reagent,  allowed 
to  dry,  and  used  as  test-paper.  Hydrochloric  acid  turns  this  paper 
brown,  and  upon  heating  the  brown  color  changes  to  blue.  (The 
paper  does  not  keep  unchanged  over  a  month.) 


ANIMAL  FLUIDS  AND  TISSUES.  437 

Phloroglucin-vanittin.  This  reagent  is  made  by  dissolving  2  parts 
of  phloroglucin  and  1  part  of  vanillin  in  30  parts  of  alcohol.  It  is 
a  very  sensitive  and  reliable  reagent  for  the  detection  of  free  hydro- 
chloric acid.  Five  drops  of  the  solution  mixed  with  an  equal  quan- 
tity of  gastric  filtrate  are  gently  heated  over  a  Bunsen  flame.  On 
complete  evaporation  a  distinct  red  color  or  tinge  appears  in  the 
presence  of  not  less  than  0.01  per  cent,  of  hydrochloric  acid.  The 
formation  of  cherry-red  crystals  indicates  the  presence  of  large 
quantities  of  the  acid.  Organic  acids  have  no  action  on  this  reagent. 

Resorcin.  This  reagent  is  equally  as  sensitive  as,  and  more  stable 
than,  phloroglucin-vanillin.  The  solution  is  obtained  by  dissolving 
5  parts  of  resublimed  resorcin  and  3  parts  of  cane-sugar  in  100  parts 
of  dilute  alcohol.  The  manner  of  testing  with  this  reagent  is  the 
same  as  described  above  for  phloroglucin-vanillin  ;  a  bright-red  tinge 
or  color  appears,  even  when  very  small  quantities  of  free  hydrochloric 
acid  are  present. 

d.  Lactic  acid.  Uffelmann's  reagent  answers  best  for  detecting 
this  acid.  It  is  made  by  adding  1  or  2  drops  of  ferric  chloride 
solution  to  10  c.c.  of  a  1  per  cent,  carbolic  acid  solution,  and  diluting 
this  solution  with  water  until  it  assumes  an  amethyst-blue  color. 
To  2  c.c.  of  this  solution  an  equal  volume  of  gastric-juice  is  added. 
In  the  presence  of  at  least  0.01  per  cent,  of  lactic  acid  the  liquid 
assumes  a  pure  yellow  color.  As  the  presence  of  too  much  hydro- 
chloric acid  (or  even  of  some  other  substances)  prevents  the  change, 
it  is  well  to  shake  (in  doubtful  cases)  10  c.c.  of  juice  with  50  c.c.  of 
ether,  evaporating  the  ethereal  solution  to  dryness,  dissolving  the 
residue  in  a  few  drops  of  water,  and  adding  to  this  solution,  which 
contains  the  lactic  acid,  the  above  reagent. 

Butyric  acid  changes  Uffelmann's  reagent  to  brownish-yellow. 
Butyric  and  acetic  acid  may  both  be  recognized  by  their  odor. 

e  Total  acidity.  This  is  best  determined  by  titration  with  an 
alkali ;  the  estimation  is  conducted  as  follows :  To  10  c.c.  of  the 
filtered  liquid  a  few  drops  of  phenol-phtalein  solution  are  added,  and 
to  the  mixture  deci-normal  potassium  hydroxide  solution  is  slowly 
added  from  a  burette  until  the  liquid  assumes-  a  slight  reddish  tint, 
which  does  not  disappear  on  stirring. 

It  is  customary  to  express  the  acidity  in  percentages,  according  to 
the  quantity  of  deci-normal  potassium  hydroxide  used.  Thus,  52 
per  cent,  acidity  would  indicate  that  every  100  c.c.  of  gastric  filtrate 
are  exactly  neutralized  by  52  c.c.  of  deci-normal  potassium  hydroxide. 

Though  the  total  acidity  is  due  to  a  mixture  of  hydrochloric  acid, 


438  PHYSIOLOGICAL  CHEMISTRY. 

organic  acids,  and  acid  salts,  it  is  frequently  expressed  as  hydrochloric 
acid.  As  1  c.c.  of  deci-normal  alkali  solution  corresponds  to  0.003637 
gramme  of  HC1,  the  number  of  c.c.  of  alkali  used  multiplied  by  the 
factor  stated,  gives  the  grammes  of  HC1  in  the  10  c.c.  of  juice  used. 
Suppose  5.2  c.c.  of  alkali  were  required;  this  would  correspond  to 
5.2  X  0.003637,  equal  to  0.0189  gramme  of  HC1  in  10  c.c.,  or  to 
0.189  per  cent. 

/.  Quantitative  determination  of  free  hydrochloric  acid.  There  are 
numerous  methods  for  the  determination  of  the  free  hydrochloric 
acid  of  the  gastric  juice.  The  more  important  are  as  follows: 

Determination  by  means  of  congo-red.  An  aqueous  solution  of 
congo-red  has  a  bright-red  color,  which  is  changed  to  blue  by  free 
acids  and  restored  to  red  by  alkalies.  Acid  salts,  such  as  acid  phos- 
phates, have  no  effect  on  this  indicator.  If,  therefore,  a  titration  of 
10  c.c.  of  filtered  gastric  juice,  to  which  enough  of  congo-red  solution 
has  been  added  to  impart  a  distinct  blue  color,  is  made  (as  above 
described  for  total  acidity)  then  the  number  of  c  c.  of  deci-normal 
potassium  hydroxide  solution  used  to  restore  the  red  color  indicates 
the  quantity  of  free  acid  present.  The  calculation  for  hydrochloric 
acid  is  made  as  above  mentioned.  This  method  gives  not  only  the 
quantity  of  free  hydrochloric  acid,  but  also  of  free  organic  acids. 
However,  the  very  small  quantities  of  organic  acids  which  are  usually 
present  in  the  gastric  filtrate  after  a  trial  breakfast  do  not  materially 
vitiate  the  results.  If  larger  quantities  of  organic  acids  are  present, 
they  must  first  be  removed  by  shaking  10  c.c.  of  gastric  juice  with 
100  c.c.  of  ether,  in  which  these  acids  are  soluble.  The  remaining 
acidity  is  due  to  free  hydrochloric  acid. 

Determination  by  means  of  phloroglucin-vanillin.  To  10  c.c.  of 
gastric  filtrate,  deci-normal  potassium  hydroxide  solution  is  added 
until  no  more  free  hydrochloric  acid  is  indicated  by  testing  a  few 
drops  of  the  liquid  with  phloroglucin-vanillin.  If,  for  instance,  no 
reaction  occurs  after  having  added  1.3  c.c.  of  potassium  hydroxide 
solution,  while  a  positive  reaction  was  yet  obtained  with  1.2  c.c.  of 
alkali  solution,  then  we  may  say  that  1.25  c.c.  of  deci-normal  alkali 
solution  were  required  for  neutralization  of  10  c.c.  of  gastric  juice, 
or  12.5  c.c.  alkali  for  100  c.c.  of  juice.  Multiplying  12.5  by  0.003637 
(the  factor  for  hydrochloric  acid)  we  find  0.045  per  cent,  of  hydro- 
chloric acid  as  the  result  of  the  determination. 

In  place  of  phloroglucin-vanillin,  the  resorcin-sugar  reagent, 
mentioned  before,  can  be  used  with  equal  advantage  as  an  indicator 
in  the  above  titration. 


ANIMAL  FLUIDS  AND  TISSUES.  439 

Leo's  method.  This  is  employed  for  very  accurate  determinations 
of  hydrochloric  acid.  It  is  based  upon  the  principle  that  free  acids 
are  fully  neutralized  by  the  addition  of  calcium  carbonate  even  at 
the  ordinary  temperature,  while  solutions  of  acid  phosphates  or  of 
other  acid  salts  retain  their  acidity. 

To  10  c.c.  of  gastric  nitrate  are  added  5  c.c.  of  concentrated  solu- 
tion of  calcium  chloride  and  a  few  drops  of  phenol-phtalein ;  titra- 
tion  is  made  with  deci-normal  potassium  hydroxide  (result  A).  To 
15  c.c.  of  a  second  portion  of  gastric  nitrate  is  added  1  gramme  of 
pure,  powdered  calcium  carbonate ;  the  mixture  is  well  shaken  and 
filtered  through  a  dry  filter.  Ten  c.c.  of  this  filtrate  are  removed,  and 
air  is  passed  through  it  in  order  to  remove  all  carbon  dioxide,  which 
interferes  with  the  use  of  phenol-phtalein  as  an  indicator.  (A 
double-bulbed  syringe,  to  one  end  of  which  a  piece  of  glass  tubing  is 
attached,  answers  well  for  this  purpose.)  Having  added  to  the 
filtrate  freed  from  carbon  dioxide  5  c.c.  of  calcium  chloride  solution 
and  phenol-phtalein,  the  titration  is  made  (result  B).  As  titration 
A  gives  the  total  acidity,  titration  B  the  acidity  due  to  acid  salts, 
therefore,  A-B  equal  the  alkali  used  for  neutralizing  the  free  acids. 
If  fatty  and  lactic  acids  are  not  present  the  result  indicates  hydro- 
chloric acid.  Should  these  acids  be  present,  they  must  first  be 
removed — the  fatty  acids  by  distillation,  the  lactic  acid  by  agitation 
with  ether. 

g.  Pepsin  and  pepsinogen.  In  case  free  acid  is  present,  10  c.c.  of 
gastric  juice  are  placed  in  a  beaker,  and  a  small  bit  of  dried  fibrin, 
or  a  lamella  of  blood  albumin  (Merck),  is  added,  and  the  beaker 
placed  in  a  thermostat  at  a  constant  temperature  of  38°  to  40°  C. 
(100°  to  104°  F.).  Pepsin  is  indicated  by  the  rapid  solution  of  the 
flake  of  albumin.  If  free  hydrochloric  is  absent,  the  juice  is  rendered 
acid  with  a  drop  of  this  acid  and  then  tested  in  the  manner  described. 

h.  Rennet  ferment  and  rennet  zymogen.  Rennet  is  tested  for  as  fol- 
lows :  Ten  c.c.  of  gastric  juice  are  exactly  neutralized  with  deci-normal 
alkali  and  mixed  with  an  equal  volume  of  neutral  unboiled,  or  better 
boiled,  milk.  The  mixture  is  placed  in  a  thermostat  at  38°  C.  (100° 
F.).  If  a  casein  coagulum  is  formed  in  ten  to  fifteen  minutes,  the 
coagulation  is  due  to  the  rennet  ferment. 

Rennet  zymogen  is  detected  thus :  Ten  c.c.  of  gastric  juice  are 
rendered  feebly  alkaline  and  mixed  with  2  c.c.  of  a  1  per  cent,  solu- 
tion of  calcium  chloride  and  10  c.c.  of  milk.  If  the  rennet  zymogen 
be  present,  a  heavy  cake  of  casein  is  precipitated  in  a  few  minutes. 

*.  Detection  of  proteids.     Of  these,  syntonin,  albumoses,  and  pep- 


440  PHYSIOLOGICAL  CHEMISTRY. 

tones  are  to  be  looked  for.  Syntonin :  The  gastric  filtrate  is  exactly 
neutralized,  whereupon  a  cloudiness  or  precipitate  is  formed,  which 
is  soluble  both  in  alkalies  and  in  acids.  Albumoses  :  These  are  pre- 
cipitated by  a  saturated  solution  of  ammonium  sulphate,  while  pep- 
tones remain  in  solution.  Peptones:  These  are  recognized  by  the 
biuret-test.  The  juice  is  rendered  strongly  alkaline  with  potassium 
hydroxide  and  a  few  drops  of  a  cupric  sulphate  solution  (1  in  1000) 
are  added.  A  red  color  indicates  the  presence  of  peptones. 

In  the  gastric  contents,  an  hour  after  an  ordinary  test-meal,  there 
is  usually  a  large  quantity  of  albumoses  and  a  smaller  amount  of 
peptone.  A  large  quantity  of  syntonin  and  a  weak  biuret  reaction 
indicate  a  weakened  proteid  digestion  and,  therefore,  a  lessened 
secretion  of  pepsin  and  hydrochloric  acid. 

j.  Detection  of  carbohydrates.  Starch  is  recognized  by  the  blue 
color  produced  by  iodine  solution  (1  iodine,  2  potassium  iodide,  100 
water).  The  reaction  is  less  marked  in  proportion  to  the  amount  of 
starch  converted  into  dextrin  and  sugar. 

Ei-yihrodextrin  gives  a  mahogany-brown  color,  and  achroodextrin 
remains  unchanged  by  the  iodine  solution.  In  strongly  acid  gastric 
contents  erythrodextrin  is  found,  while  in  cases  in  which  hydrochloric 
acid  is  absent  achroodextrin  is  almost  exclusively  present.  In  as 
much  as  sugar  is  present  in  the  test-meal  itself,  it  is  useless  to  test 
for  this  substance. 

Bile,  secreted  by  the  liver,  is  a  thin,  transparent  liquid  of  a  golden- 
yellow  color,  and  a  specific  gravity  of  1.020 ;  it  has  a  very  bitter  taste 
and  an  alkaline  reaction  ;  it  varies  widely  in  composition,  the  total 
solids  ranging  from  9  to  17  per  cent.,  being  always  highest  after  a 
meal ;  its  composition,  moreover,  is  highly  complex  ;  the  following  is 
an  average  of  five  analyses  of  bile  from  subjects  with  healthy  livers : 

Water        .        . 91.68  per  cent. 

Mucus  pigment .  1.29  " 

Taurocholate  of  sodium 0.87  " 

Glycocholate  of  sodium 3.03  " 

Fat 0.73  " 

Soaps 1.39  " 

Cholesterin 0  35  " 

Lecithin 0  53  " 

Bile  obtained  after  death  is  of  a  brownish-yellow  color ;  freed  from 
mucus  it  will  remain  undecomposed  for  an  almost  indefinite  period. 
The  mucus  may  be  separated  by  the  addition  of  diluted  alcohol  and 
subsequent  filtration. 


ANIMAL  FLUIDS  AND  TISSUES.  441 

The  quantity  of  bile  discharged  daily  by  a  grown  person  may  be 
put  at  forty  ounces,  but  a  considerable  quantity  of  this  discharged 
bile  is  reabsorbed  in  a  changed  form  by  the  intestines ;  only  a  small 
amount  of  bile  matters  (in  a  decomposed  state,  however)  is  discharged 
by  the  feces. 

The  functions  of  bile  have  been  stated  in  the  previous  chapter. 

Biliary  pigments.  Of  these  four  are  known,  but  it  is  probable  that 
more  exist.  Bilirubin,  C16H18N2O3,  is,  when  amorphous,  an  orange- 
yellow  powder ;  when  crystalline,  it  forms  red  prisms.  It  is  sparingly 
soluble  in  water,  alcohol,  and  ether,  readily  soluble  in  hot  chloroform 
and  carbon  disulphide.  When  treated  with  a  mixture  of  concentrated 
nitric  acid  and  sulphuric  acid  it  turns  first  green,  then  blue,  violet,  red, 
and  finally  yellow.  This  reaction,  known  as  Gmelin's  test,  is  used  for 
the  detection  of  bile-pigments  in  urine  and  other  fluids.  (See  Plate 
VIII.,  7.) 

Biliverdin,  C32H36N4O8,  is  a  green  powder  existing  in  green  biles; 
it  responds  to  Gmelin's  test. 

Biliary  acids.  G-lycocholic  acid,  C26H43NO6,  and  taurocholic  acid, 
C26H45NO7S,  exist  as  sodium  salts  in  the  bile  of  man  and  most 
animals.  Both  salts  may  be  obtained  as  colorless  crystals,  which 
dissolve  in  water,  forming  solutions  of  an  acid  reaction  and  an 
intensely  bitter  taste.  Both  acids  are  easily  decomposed  by  heating 
with  alkalies  or  with  dilute  acids,  also  by  the  action  of  putrefying 
material  or  by  the  chemical  changes  taking  place  in  the  intestines. 
In  all  these  cases  is  formed  cholic  add,  C24H40O5,  and  a  second  pro- 
duct, which  in  the  case  of  glycocholic  acid  is  glycocol,  C2H5NO2,  and 
in  the  case  of  taurocholic  acid  taurine,  C2H7NO3S. 

Pettenkofer's  test.  The  biliary  acids  and  their  salts  show  a  charac- 
teristic reaction  known  as  Pettenkofer's  test.  This  reaction  is  shown 
by  adding  very  little  cane-sugar  to  the  liquid  substance  under  exam- 
ination, and  adding  concentrated  sulphuric  acid  in  such  a  manner 
that  the  temperature  does  not  rise  above  70°  C.  (158°  F.).  In  the 
presence  of  biliary  acids  a  beautiful  cherry- red  color  is  developed, 
which  gradually  changes  to  dark  reddish-purple.  (See  Plate 

Yin.,  s.) 

The  bile  acids  are,  however,  not  the  only  substances  which  show  the  above 
reaction,  and,  therefore,  it  becomes  in  many  cases  necessary  to  separate  the 
bile  acids  from  other  organic  matter.  This  separation  is  accomplished  by 
evaporating  the  substance  under  examination  (urine,  for  instance),  after  having 
been  mixed  with  a  small  quantity  of  coarse  animal  charcoal,  to  dryness  at 


442  PHYSIOLOGICAL  CHEMISTRY. 

100°  C.  (212°  F.).  The  residue  is  extracted  with  absolute  alcohol,  the  filtered 
alcoholic  solution  is  again  partially  evaporated,  and  mixed  with  10  volumes  of 
absolute  ether.  The  biliary  acids  are  soluble  in  alcohol,  but  not  in  ether,  or 
in  ether  containing  one-tenth  of  alcohol.  After  standing  an  hour  or  two  the 
biliary  acids  will  form  a  deposit,  which  is  collected  on  a  small  filter,  dissolved 
in  a  little  water,  and  mixed  with  a  few  drops  of  a  strong  solution  of  sugar. 
Upon  the  addition  of  sulphuric  acid,  with  the  precaution  above  mentioned,  the 
characteristic  colors  will  indicate  the  presence  of  the  bile  acids. 

Experiment  67.  Evaporate  ox-bile  to  a  thick  syrup,  digest  it  with  5  parts  of 
pure,  cold  alcohol  for  two  hours,  and  filter.  Mix  the  filtrate,  which  contains 
sodium  glycocholate  and  taurocholate,  with  freshly  prepared  animal  charcoal, 
boil  and  filter ;  evaporate  to  dryness  in  a  water-bath,  redissolve  in  the  smallest 
possible  amount  of  pure  alcohol,  and  add  ether  until  the  solution  becomes 
markedly  turbid.  A  white,  crystalline  mass  is  deposited  in  a  few  hours  or  days ; 
this  is  known  as  Plattner's  crystallized  bile,  and  is  a  mixture  of  the  two  sodium 
salts  mentioned. 

Dissolve  the  mass  in  a  small  volume  of  water,  adding  a  little  ether  and  then 
dilute  sulphuric  acid;  glycocholic  acid  crystallizes  out  in  shining  needles. 

Cholesterin,  C26H43.OH.  This  substance  has  been  classed  by 
physiologists  among  the  fats,  because  it  is  greasy  and  soluble  in 
ether,  but  its  chemical  constitution  is  that  of  an  alcohol.  It  is  found 
chiefly  in  bile,  but  also  in  blood,  nerve-tissue,  brain,  contents  of  the 
intestines,  feces,  etc. ;  its  presence  in  certain  vegetables,  as  peas,  beans, 
etc.,  has  also  been  demonstrated. 

Cholesterin  crystallizes  in  colorless,  silky  needles,  which  are  insolu- 
ble in  water,  alkalies,  and  dilute  acids,  but  soluble  in  ether.  It 
sometimes  forms  in  the  organism  solid  masses,  known  as  biliary  cal- 
culi or  gall-stones,  some  of  which  are  almost  pure  cholesterin. 

Tests  for  cholesterin: 

1.  Evaporated  with  nitric  acid  it  gives  a  yellow  mass,  which  turns 
brick -red  on  addition  of  ammonia. 

2.  Mixed  in  the  dry  state  with  strong  sulphuric  acid,  it  produces 
a  blue-red  or  violet  color  on  addition  of  chloroform,  the  color  chang- 
ing to  green  on  exposure  to  air. 

3.  Evaporated  with  a  mixture  of  2  volumes  of  sulphuric  acid  and 
1  volume  of  ferric  chloride  solution,  it  turns  violet. 

Lecithins,  C44H90NPO9  or  C42H84NPO9.  Lecithin,  one  of  the  con- 
stituents of  bile,  is  a  member  of  the  group  of  substances  generally 
termed  phosphorized  fats  or  lecithins.  These  bodies  are  highly  com- 
plex in  composition,  and  may  be  looked  upon  as  fats  formed  from 
glycerin,  in  which  hydrogen  atoms  are  replaced  by  the  radicals  of 
phosphoric  and  fatty  acids. 


ANIMAL  FLUIDS  AND  TISSUES.  443 

Pancreatic  juice.  There  is  no  thoroughly  reliable  analysis  of  this 
highly  complex  liquid  on  record.  It  contains  from  3  to  6  per  cent, 
of  solids,  two-thirds  of  which  are  of  organic,  one-third  of  inorganic 
nature.  Among  the  organic  constituents  are  a  number  (certainly 
two,  probably  four)  of  enzymes:  1.  Amylopsin  converts  starch  into 
sugar  (this  action  is  more  energetic  than  that  of  ptyalin) ;  2.  Trypsin 
converts  proteids  into  peptones  (this  action  takes  place  in  alkaline, 
but  not  in  acid  solution,  as  in  case  of  pepsin  ;  3.  Steapsin  decomposes 
fats  into  glycerin  and  fatty  acids ;  4.  An  enzyme  of  which  little  is 
known,  capable  of  emulsifying  neutral  fats. 

Peces  consist  of  that  portion  of  the  food  which  has  not  been  taken 
into  the  system  by  absorption,  and  is  discharged  from  the  body  mixed 
with  some  of  the  products  of  the  biliary  and  intestinal  secretions. 
The  odor  depends  largely  on  two  substances,  indol  and  skatol,  and  to 
a  less  degree  on  the  valerianic  and  butyric  acids  and  the  hydrogen 
sulphide  present.  Indol,  C8H7N,  belongs  to  the  aromatic  compounds, 
and  is  one  of  the  products  of  the  putrefaction  of  albumin.  The 
quantity  of  feces  passed  depends  on  the  nature  of  the  food  taken 
and  on  the  energy  of  the  digestive  powers.  A  grown  person,  in 
normal  condition,  discharges  from  7  to  9  ounces  daily.  An  approxi- 
mate analysis  of  the  feces  of  a  healthy  adult  shows : 

Water 77.3  per  cent. 

Mucin 2.3 

Proteids 5.4        " 

Extractives 1.8        " 

Fats 1.5 

Salts 1.8 

Resinous,  biliary,  and  coloring  matters      .        .  5.2        " 

Insoluble  residue  of  food    ......  4.7         " 

Bone  is  chemically  distinguished  from  other  tissues  by  the  large 
quantity  of  inorganic  salts  which  it  contains.  Dried  bones  contain 
about  31  per  cent,  of  organic  matter  combined  with  69  per  cent,  of 
mineral  matter.  Different  bones  (and  even^  different  parts  of  the  same 
bone)  of  the  same  person  differ  somewhat  in  composition;  more- 
over, the  bones  of  a  child  contain  somewhat  more  of  organic  matter 
than  those  of  a  grown  person,  as  may  be  shown  by  the  following 
analyses  of  the  corresponding  bone  in  children  and  a  grown  person  : 

Child  one  year.  Child  five  years.  Man  twenty-five  years. 

Organic  matter,                43.42  per  cent.  32.29  per  cent.  31.17  per  cent. 

Tricalcium  phosphate,     48.55        "  59.74        "  58.95        " 

Magnesium  phosphate,      1.00        "                1.34        "  1.30        " 

Calcium  carbonate,            5.79        "                6.00        "  7.08        " 

Soluble  salts,                      1.24        "                0.63        "  1.50        " 


444  PHYSIOLOGICAL  CHEMISTRY. 

Frequently  human  bones  contain  calcium  fluoride,  which  substance, 
to  the  amount  of  1  to  2  per  cent,,  is  a  normal  constituent  of  the  bones 
of  many  animals.  The  organic  matter  of  bone  is  called  ossein,  and 
is  a  mixture  of  collagen,  elastin,  and  an  albuminoid  existing  in  the 
bone-cells.  Collagen  is  a  nitrogenous  substance,  insoluble  in  water, 
but  forming  when  treated  with  it  under  the  influence  of  heat  and 
pressure,  gelatin,  an  amorphous,  tasteless,  translucent  substance,  which 
swells  up  in  boiling  water,  forming  on  cooling  a  soft  jelly ;  an  impure 
form  of  gelatin  is  common  glue. 

Teeth  consist  of  three  distinct  tissues,  viz.,  dentine,  forming  the 
chief  mass,  in  its  interior  being  the  pulp  cavity;  enamel,  investing 
the  crown  and  extending  some  distance  down  the  neck ;  and  cement, 
covering  the  fangs.  The  composition  of  cement  is  almost  the  same  as 
that  of  bone,  its  organic  and  inorganic  constituents  having  the  rela- 
tive proportions  of  30  :  70. 

Dentine  contains  less  water  than  bone  and  is  also  poorer  in  organic 
matter.  The  following  table  gives  the  composition  of  the  dentine  of 
an  adult  woman  and  man  respectively : 

Woman.  Man. 

Organic  matter — ossein  and  vessels    .        .         .  27.61  20.42 

Calcium  phosphate   ......  66.72  67.54 

Calcium  carbonate 3.36  7.97 

Magnesium  phosphate 1.08  2.49 

Soluble  salts,  chiefly  sodium  chloride        .         .  0.83  1.00 

Fat 0.40  0.58 

Enamel  is  distinguished  by  the  very  small  proportion  of  water  and 
organic  matter  contained  in  it.  Its  average  composition  may  be  thus 
stated: 

Water  and  organic  matter 3.6 

Calcium  phosphate  and  traces  of  fluoride      ....  86.9 

Magnesium  phosphate 1.5 

Calcium  carbonate         ........  8.0 

Tartar  is  the  name  given  to  the  substance  which  deposits  from 
alkaline  saliva  on  the  teeth.  It  is  of  a  grayish,  yellowish,  or  brown- 
ish color,  and  consists  chiefly  of  calcium  phosphate,  with  a  little 
carbonate,  but  contains  also  some  organic  matter,  salts  of  the  alkalies, 
and  silica. 

Hair,  nails,  horns,  hoofs,  feathers,  epithelium  are  nearly  iden- 
tical in  composition.  They  all  contain  a  nitrogenous  substance, 
termed  keratin,  which  is  probably  not  a  distinct  chemical  compound, 


MILK.  445 

but   a   mixture   of  several   substances   similar  in  composition  and 
properties. 

Mucus  is  secreted  by  the  various  mucous  membranes,  and  is  found 
in  saliva,  bile,  connective  tissues,  feces,  urine,  etc.  When  pure  it 
forms  a  clear,  translucent  or  viscid  mass ;  it  contains  a  substance 
termed  mucin,  which  swells  up  in  water,  and  readily  dissolves  in 
water  containing  an  alkali ;  from  these  solutions  it  is  precipitated  by 
acetic  acid. 

Muscles  contain  fibrin,  albumin,  myosin,  kreatin,  C4H9N3O2, 
sarkin,  C5H4N4O,  xanthin,  C5H4N4O2,  uric  acid,  glucose,  inosite, 
lactates,  and  salts. 

Kreatin,  sarkin,  and  xanthin  are  substances  formed  in  the  organism 
by  oxidation  of  proteids,  and  may  be  looked  upon  as  compound  ureas 
or  substances  formed  as  intermediate  products  of  the  final  conversion 
of  proteids  into  urea,  carbon  dioxide,  water,  etc.  These  substances 
may  indeed  be  decomposed  artificially  in  such  a  manner  that  urea  is 
produced  as  one  of  the  products  of  decomposition. 

Brain  consists  of  so  many  individual  parts  that  the  analysis  of  it 
as  a  whole  is  of  little  value,  and  to  separate  these  parts  successfully  is 
a  task  not  yet  accomplished.  Brain,  as  a  whole,  contains  cerebrin, 
lecithin,  cholesterin,  protagon,  and  many  other  substances,  some  of 
which  are  distinguished  by  the  large  quantity  of  phosphorus  they 
contain. 

54.  MILK. 

Properties  and  composition.  Milk  is  the  secretion  of  the  mam- 
mary glands,  the  presence  of  which  is  characteristic  of  the  class  of 

QUESTIONS. — 521.  What  three  kinds  of  matter  are  found  as  constituents  of 
the  animal  body,  and  how  can  they  be  determined  quantitatively?  522.  Men- 
tion the  chief  constituents  of  blood,  and  state  those  which  predominate  in  serum 
and  in  the  corpuscles  respectively.  523.  What  substances  cause  the  clotting 
of  blood,  and  what  explanation  can  be  given?  524.  How  may  blood-stains  be 
recognized?  525.  What  is  the  active  principle  of  saliva,  and  how  does  it  act 
on  starch  ?  526.  State  the  composition  of  gastric  juice,  and  explain  its  physio- 
logical action.  527.  State  the  general  properties  of  bile,  and  mention  its  chief 
constituents.  528.  Give  Gmelin's  test  for  biliary  pigments,  and  Pettenkofer's 
test  for  biliary  acids.  What  precautions  are  necessary  in  using  the  latter  test? 
529.  What  is  cholesterin  ?  State  its  properties  and  reactions.  530.  Mention 
the  principal  constituents  of  muscles,  bone,  teeth,  and  hair. 


446  PHYSIOLOGICAL  CHEMISTRY. 

animals  known  as  mammalia.  The  milk  of  different  animals  differs 
somewhat  in  composition,  but  it  always  contains  all  the  constituents 
necessary  for  a  normal  development  of  the  various  tissues,  liquids, 
organs,  etc.,  of  the  young  mammal,  which  generally  feeds  exclusively 
upon  milk  for  a  shorter  or  longer  period  of  its  early  life. 

Milk  is  an  opaque,  aqueous  solution  of  casein,  albumin,  lactose,  and 
inorganic  salts,  holding  in  suspension  small  globules  of  fat,  invested, 
most  likely,  with  coatings  of  casein  or  with  some  other  albuminous 
envelope.  The  reaction  of  woman's  milk  and  that  of  the  herbivora 
is  normally  alkaline,  but  that  of  carnivora  is  acid.  Its  specific 
gravity  ranges  from  1.029  to  1.033,  but  may  in  extreme  cases  vary 
between  1.018  and  1.045. 

The  average  composition  of  various  kinds  of  milk  is  given  below, 
but  it  must  be  remembered  that  milk  not  only  differs  in  certain  species, 
but  also  in  the  same  animal  at  different  times ;  for  instance,  the 
quality  and  quantity  of  food  taken,  as  also  various  physiological 
changes,  have  decided  influence  upon  the  milk  secreted. 

Human  milk.  Cow's  milk. 


Variations.         Average. 

Variations. 

Average. 

Water   . 

90.8  to  85.3        88.50 

90.2  to  83.7 

86.95 

Casein  and  albumin 

1.4  to 

2.5 

2.00 

3.3  to 

5.5 

4.40 

Fat  (butter)  . 

3.0  to 

3.8 

3.40 

2.8  to 

4.5 

3.65 

Lactose 

4.5  to 

7.0 

5.75 

3.0  to 

5.5 

4.25 

Inorganic  salts 

0.3  to 

0.4 

0.35 

0.7  to 

0.8 

0.75 

Goat. 

Sheep. 

Ass. 

Mare. 

Cream. 

Water    . 

86.0 

83.3 

90.6 

90.6 

50 

to  70 

Casein  and  albumin 

3.8 

5.4 

2.7 

2.2 

5 

to    4 

Fat  (butter)  . 

5.2 

5.3 

1.0 

1.1 

41 

to  22 

Lactose  . 

4.3 

5.2 

5.3 

5.8 

3 

to    3 

Inorganic  salts 

0.7 

0.8 

0.4 

0.3 

0.7 

to    0.7 

Skimmed 
milk. 

Condensed   «ntt 
milk.        Butter. 

Buttermilk. 

Curd, 

Whey. 

Water    . 

89.6 

25 

15.0 

91.0 

59.4 

93.8 

Casein  and  albumin 

4.2 

14 

2.2 

3.7 

27.7 

0.8 

Fat  (butter)    . 

1.0 

10 

82.0 

0.8 

6.4 

0.3 

Lactose  . 

4.4 

491 

0.3 

3.8 

5.0 

4.5 

Inorganic  salts 

0.8 

2 

0.5 

0.7 

1.5 

0.6 

The  inorganic  salts  consist  chiefly  of  calcium  or  sodium  phosphate 
and  sodium  and  potassium  chloride,  but  contain  also  some  magnesium 
and  iron.  The  proteids  consist  mainly  of  casein  with  some  albumin, 
the  proportion  being  about  as  6  to  1 . 

Besides  the  constituents  mentioned  in  the  above  analyses,  milk  also 
contains  a  very  small  quantity  of  extractives,  among  which  are  found 

1  Including  cane-sugar  added  by  the  manufacturer. 


MILK.  447 

peptone,  kreatin,  leucin,  etc.     The  principles  which  give  to  milk  its 
peculiar  odor  have  not  yet  been  conclusively  pointed  out. 

The  gaseous  constituents  of  milk  are  mainly  carbon  dioxide,  oxygen, 
and  nitrogen.  100  volumes  of  milk  contain  of  carbon  dioxide  7.6, 
of  oxygen  0.1,  of  nitrogen  0.7  volumes. 

Changes  in  milk.  Soon  after  milk  leaves  the  animal  system 
changes  take  place  which  are  either  of  a  physical  or  chemical  nature. 
The  first  change  in  milk,  when  allowed  to  stand  for  a  few  hours,  is 
a  separation  of  the  suspended  fat  globules  toward  the  upper  part  of 
the  liquid,  which  gradually  becomes  loaded  with  fat,  forming  a  dis- 
tinct layer  over  the  liquid.  This  upper  layer  having  a  slightly 
yellowish  color  (cream  color)  is  cream,  the  watery  liquid  below  hav- 
ing a  bluish-white  color  is  skimmed  milk. 

Another  change  taking  place  in  milk  (rarely  after  a  few  hours, 
but  generally  after  a  day  or  a  few  days)  is  the  coagulation  of  casein, 
which  takes  place  both  in  the  cream  and  in  the  skimmed  milk,  con- 
verting the  whole  into  a  thick,  semi-liquid  mass,  which  gradually 
separates  into  a  solid  white  curd,  and  a  thin,  transparent  milk-serum 
or  whey. 

The  coagulation  of  the  casein  is  caused  by  lactic  acid,  produced  by 
the  so-called  lactic  fermentation  of  lactose.  The  ferments  causing 
this  fermentation  are  undoubtedly  floating  in  the  air,  as  it  is  possible 
to  prevent  the  decomposition  of  milk-sugar  for  a  considerable  length 
of  time  by  taking  proper  precautions  for  destroying  and  excluding 
them.  Simultaneously  with  the  coagulation  of  milk  the  alkaline 
reaction  becomes  acid  and  the  sweet  taste  gradually  more  and  more 
sour. 

These  changes  in  milk  can,  to  some  extent,  be  artificially  produced, 
hindered,  and  controlled.  Thus,  the  casein  may  be  precipitated  by 
the  addition  of  rennet  or  acetic  acid  (or  any  mineral  acid)  and  heating. 
The  decomposition  of  the  milk-sugar  and  with  it  the  "  curdling  "  may 
be  prevented — 1,  by  chemical  treatment  with  alkaline  salts  or  anti- 
septics ;  2,  by  physical  treatment,  such  as  cooling  or  icing,  boiling 
and  aeration  ;  3,  by  condensation  or  evaporation,  with  or  without  the 
addition  of  a  preservative  agent.  All  these  systems  of  preservation, 
however,  are  subject  to  serious  disadvantages  because  they  either  inter- 
fere with  the  natural  constitution  and  properties  of  the  milk,  or 
because  they  serve  their  purpose  for  too  limited  a  time. 

The  addition  of  alkalies  such  as  lime-water,  sodium  carbonate  or 
bicarbonate,  does  not  prevent  the  lactic  fermentation,  but  prevents 


448  PHYSIOLOGICAL  CHEMISTRY. 

the  action  of  the  liberated  acid  on  the  casein  by  forming  a  lactate  of 
calcium  or  sodium. 

Of  antiseptics,  salicylic  acid  has  been  used  with  good  results  (2 
grains  to  a  pint),  but  it  should  be  remembered  that  salicylic  acid  is 
not  absolutely  harmless. 

Of  all  preservatives,  cold  is  the  most  efficient  and  least  objection- 
able, and  milk  when  cooled  to  within  a  few  degrees  of  the  freezing- 
point  may  be  kept  for  eight  to  twelve  days  sweet  and  without  change. 

The  condensation  of  milk  is  effected  either  simply  by  evaporating 
(generally  in  vacuum  pahs)  a  portion  of  the  water,  or  by  first  dis- 
solving in  it  a  certain  quantity  of  sugar  (generally  cane-sugar)  and 
then  evaporating  to  the  consistence  of  a  thick  syrup,  which  is  placed 
in  suitable  air-tight  jars.  The  sugar  which  is  added  serves  as  an 
additional  preventive  of  decomposition. 

The  following  gives  the  constituents  of  milk  which  may  be  obtained 
from  it  by  mechanical  processes  after  it  has  been  changed  as  described 
above : 

Cream,  20j  Butter 3.5  parts. 

I  Buttermilk 16.5      " 

Skimmed  milk,  80  {Curd 8'°     " 

I  Whey 72.0     " 

Butter.  Even  in  the  thickest  varieties  of  cream  there  is  no 
cohesion  between  the  fat  globules,  whilst  in  butter  the  fat  has  actually 
cohered.  This  change  is  accomplished  by  violently  agitating  (churn- 
ing) the  cream,  when  the  fat  particles  gradually  combine  with  each 
other,  whilst  the  liquid  (buttermilk)  separates. 

Chemically,  butter  is  a  milk-fat,  .a  mixture  of  different  fats  or 
glycerides  of  the  fatty  acids,  chiefly  palmitic  and  oleic  acids,  with 
small  quantities  of  butyric,  caprionic,  caprylic,  and  stearic  acids  ;  it 
always  contains  a  certain  proportion,  15  or  16  per  cent.,  of  water, 
besides  traces  of  casein,  salts,  coloring  matter,  etc. 

For  curing  butter,  common  salt  is  often  used ;  the  quantity  added 
should  not  exceed  5  per  cent. 

The  composition  of  buttermilk  has  been  given  above;  when  freshly 
obtained  from  sweet  cream  it  is  a  pleasant  drink  and  a  wholesome  food. 

Cheese  consists  mainly  of  casein,  milk-fat,  water,  and  inorganic 
salts ;  these  constituents  vary  as  follows  : 

Water 61  to  28  parts. 

Casein        .         .         . 15  to  35     " 

Fat 20  to  30     " 

Salts.  4  to    7      " 


MILK.  449 

Cheese  is  made  either  from  pure  milk,  from  skimmed  milk,  or  from 
a  mixture  of  milk  and  cream,  and  accordingly  varies  considerably  in 
composition.  Practically,  cheese  is  made  by  causing  milk  to  coagulate 
(either  by  allowing  it  to  stand  or  by  the  addition  of  rennet,  acids,  or 
other  substances),  and  separating  the  curd  (casein  and  fat)  from  the 
whey  by  mechanical  means,  such  as  filtering  and  pressing.  The  curd 
is  placed  in  suitable  moulds  and  afterward  allowed  to  stand  or  "  ripen  " 
for  a  shorter  or  longer  period.  The  process  of  ripening  is  a  partial 
decomposition  (decay  and  putrefaction)  of  the  casein,  and  the  value  of 
cheese  depends  mainly  upon  the  nature  of  the  products  formed  during 
this  decomposition. 

Adulterations  of  milk.  Of  these,  the  most  commonly  practised 
are  removal  of  cream,  addition  of  water,  or  both.  Sometimes  sodium 
carbonate,  sugar,  and  even  chalk  are  added,  but  these  latter  adultera- 
tions are  fortunately  but  rarely  practised  by  milk-dealers.  The  ques- 
tion whether  or  not  milk  has  been  tampered  with  is  generally  decided 
by  ascertaining  whether  cream  has  been  removed  or  water  added.  It 
is,  therefore,  chiefly  the  quantity  of  total  solids  which  has  to  be  de- 
termined in  order  to  decide  the  purity  of  milk.  But  it  has  been  shown 
by  the  above  tables  of  milk  analyses  that  the  quantity  of  these  solids 
varies  considerably,  and  a  minimum  of  total  solids  should,  therefore, 
be  adopted  legally.  While  no  such  minimum  quantity  is  officially 
recognized  in  many  States  of  this  country,  it  is  safe  to  say  that  milk 
containing  less  than  1 1  per  cent,  of  total  solids  may  be  looked  upon 
as  adulterated.  (The  above  given  lowest  quantity  of  9.8  per  cent, 
of  total  solids  in  cow's  milk  is  very  abnormal.)  The  methods  for 
detecting  such  fraud  will  now  be  considered. 

Testing-  milk.  There  is,  unfortunately,  no  instrument  which  will 
indicate  the  purity  or  quality  of  milk  directly.  An  instrument  used 
for  that  purpose,  and  known  as  the  lactometer,  is  simply  a  hydrometer 
which  indicates  the  specific  gravity  of  milk.  There  are,  however,  in 
milk  substances  which  have  a  tendency  to  increase  the  specific  gravity, 
such  as  lactose,  salts,  and  casein,  whilst  there  is  at  the  same  time  one 
substance,  the  fat,  which  is  specifically  lighter  than  water.  The 
specific  gravity  of  milk  ranges  from  1.027  to  1.034,  the  average  being 
about  1.030.  If  water  be  added  to  milk,  the  specific  gravity  will 
become  lower,  but  the  same  effect  may  be  obtained  by  adding  fat  or 
cream.  Again,  if  cream  be  removed,  the  specific  gravity  will  be 
higher,  and  in  order  to  bring  the  milk  back  to  the  standard  of  1.030, 

29 


450  PHYSIOLOGICAL  CHEMISTRY. 

water  may  be  added.  In  other  words,  cream  may  be  removed  from, 
and  water  added  to,  the  same  milk  and  the  specific  gravity  will  be 
unchanged ;  or  a  natural  milk  containing  large  quantities  of  fat  has 
the  same  specific  gravity  as  a  poorer  milk  to  which  water  has  been 
added. 

These  facts  show  that  the  lactometer  alone  is  of  no  value  whatever 
in  milk  analysis,  although  it  is  useful  when  the  quantity  of  cream 
has  also  been  determined.  This  is  generally  accomplished  by  the 
so-called  creamometer,  a  glass  tube  or  glass  cylinder  about  one  foot 
long,  half  an  inch  in  diameter,  and  graduated  into  100  parts  by 
volume,  the  0  being  about  an  inch  from  the  top.  The  tube  is  filled 
with  milk  to  the  0  and  set  aside  for  12  or  18  hours,  when  the  line  of 
demarcation  between  the  cream  and  the  liquid  below  is  ,well  defined 
and  may  be  easily  read  off. 

The  quantity  of  cream  varies  from  8  to  20  per  cent.,  but  should 
not  fall  below  10  per  cent.  Milk  which  shows  a  large  quantity  of 
cream  (15  to  18  per  cent.)  may  fall  considerably  below  1.030  in 
specific  gravity,  but  if  there  is  little  cream  (8  to  10  per  cent.)  and 
the  milk  shows  a  low  specific  gravity,  there  can  be  little  doubt  that 
it  has  been  tampered  with. 

There  are  a  number  of  other  instruments,  the  so-called  "  lactoscopes"  used  for 
the  determination  of  cream,  the  operations  of  which  are  based  on  the  fact  that 
milk  rich  in  cream  is  a  much  more  opaque  (or  more  white)  fluid  than  that  from 
which  cream  has  been  taken  or  to  which  water  has  been  added. 

The  above  methods  of  determining  the  purity  of  milk,  although 
answering  for  ordinary  purposes,  are  absolutely  insufficient  for  scien- 
tific purposes  or  as  evidence  upon  which  to  base  legal  proceedings. 
In  such  cases  a  complete  analysis,  including  the  exact  determination 
of  total  solids  and  of  various  constituents,  is  required. 

Analysis  of  milk.  The  total  solids  are  determined  by  placing  a 
weighed  quantity  (from  5  to  10  c.c.)  of  the  well-mixed  milk  in  a 
weighed  platinum  dish  and  heating  for  several  hours  in  a  water-bath 
until  no  more  weight  is  lost.  The  loss  in  weight  represents  the  water, 
the  weight  of  the  residue  the  total  solids.  The  fat  is  determined  by 
extracting  the  solid  residue  repeatedly  with  warm  ether,  filtering  this 
solution  through  a  small  filter,  which  is  to  be  well  washed  with  ether, 
and  evaporating  the  ethereal  solution  in  a  weighed  platinum  dish. 

Milk-sugar  is  next  determined  by  treating  the  residue  (from  which 
fat  has  been  extracted)  with  hot  diluted  alcohol ;  lactose  and  a  few 
soluble  salts  enter  into  solution ;  the  liquid  evaporated  to  dry  ness  in 


MILK.  451 

a  weighed  dish  gives  the  quantity  of  sugar  plus  some  salts.  Upon 
igniting  the  milk-sugar  a  residue  of  salts  is  left,  which  is  also  weighed, 
and  this  weight  deducted  from  the  first  one. 

Casein.  The  residue  now  left  (after  treatment  with  ether  and  alco- 
hol) contains  chiefly  casein  with  some  albumin  and  salts.  If  any 
casein  should  have  been  washed  upon  the  filters  accidentally,  it  has 
to  be  transferred  back  to  the  dish,  the  contents  of  which  are  dried 
and  weighed.  By  burning  off  the  casein  and  re  weighing  the  dish 
plus  the  salts,  the  quantity  of  the  casein  is  determined. 

The  remaining  salts  added  to  those  previously  obtained  from  the 
alcoholic  solution  form  the  total  ash  or  inorganic  solids,  an  analysis  of 
which  may  be  made  according  to  the  methods  given  heretofore. 

Casein  may  also  be  determined  directly  by  precipitating  it  from 
milk,  by  the  addition  of  acetic  acid  and  boiling.  The  precipitated 
casein  is  filtered  off,  and  has  to  be  well  washed,  first  with  water,  and 
then  with  ether,  as  it  contains  most  of  the  fat. 

Experiment  68.  a.  Determine  the  specific  gravity  of  milk,  cream  and  skimmed 
milk  by  means  of  the  lactometer  (a  urinometer  answers  the  purpose). 

b.  Acidulate  some  skimmed  milk  with  acetic  acid,  notice  the  coagulation  of 
the  casein,  and  separate  it  from  the  whey  by  filtering  through  paper  or  cloth, 
using  some  pressure  to  expel  most  of  the  liquid. 

c.  Test  the  casein  by  heating  with  nitric  acid  (yellow  color),  by  using  Mil- 
Ion's  reagent  (purple-red  color),  by  warming  gently  on  the  water-bath  with  con- 
centrated hydrochloric  acid  (violet-colored  solution),  by  warming  gently  with 
water  and  a  few  drops  of  potassium  hydroxide,  when  a  solution  is  obtained 
from  which  the  casein  is  reprecipitated  on  neutralizing  with  acetic  acid. 

d.  Test  the  whey  for  milk-sugar  by  heating  with  Fehling's  solution  (red  pre- 
cipitate), by  applying  Moore's  test,  i.  e.,  heating  with  potassium  hydroxide 
(brown  color),  and  by  heating  with  solution  of  picric  acid  and  potassium 
hydroxide  (reddish-brown  color). 

e.  Determine  the  constituents  of  milk  quantitatively  by  using  the  directions 
given  above. 

QUESTIONS.— 531.  Mention  the  five  principal  constituents  of  milk.  532.  Give 
the  average  composition  of  human  and  of  cow's  milk.  533.  What  compounds 
constitute  milk-ashes  ?  534.  What  physical  and  what  chemical  changes  does 
milk  suffer  on  standing?  535.  What  acid  is  formed  in  milk  on  standing,  and 
how  does  this  acid  act  on  the  casein?  536.  Describe  the  processes  used  for 
preventing  the  decomposition  of  milk.  What  are  their  advantages  and  their 
disadvantages?  537.  Give  approximately  the  quantities  of  the  chief  com- 
ponents of  cream,  skimmed  milk,  butter,  buttermilk,  curd,  whey,  and  cheese, 
and  state  how  these  substances  are  obtained.  538.  Why  does  the  specific 
gravity  of  milk  not  indicate  its  purity  and  richness?  539.  Describe  the 
advantages  of  the  combined  use  of  the  lactometer  and  creamometer  in  testing 
milk.  540.  Give  a  process  for  the  complete  quantitative  analysis  of  milk. 


452 •  PHYSIOLOGICAL  CHEMISTRY. 

55.    URINE  AND  ITS  NORMAL   CONSTITUENTS. 

Secretion  of  urine.  It  has  been  explained  in  a  former  chapter 
how  blood  absorbs  the  digested  food  as  chyle,  how  this  is  acted  upon 
by  the  atmospheric  oxygen  in  the  lungs;  and  how  this  arterial  blood, 
whilst  passing  through  the  system,  deposits  proteids  and  other  sub- 
stances, receiving  in  exchange  the  products  formed  by  the  oxidation  of 
the  various  tissues.  These  products  are  either  gases  (chiefly  carbon 
dioxide),  liquids  (chiefly  water),  or  solids  held  in  solution  by  the 
water.  These  waste  solids  must  necessarily  be  eliminated  from  the 
system,  and  the  organs  which  accomplish  this  result  are  the  kidneys. 

The  process  of  separating  the  waste  materials  from  the  blood  is  chiefly  of  a 
physical  nature,  partly  a  transudation  or  nitration,  and  partly  a  diffusion  or 
osmose.  The  conditions  essential  for  such  an  exchange  are  given  in  the 
kidneys.  Blood  is  separated  by  delicate  membranes  from  a  thin,  aqueous, 
saline  solution ;  the  interchange  taking  place  is  chiefly  a  passage  of  the  waste 
crystalline  products  of  the  blood  into  the  aqueous  solution,  which  is  thereby 
gradually  converted  into  urine,  that  liquid,  which  is  finally  discharged,  carry- 
ing off  nearly  the  total  quantity  of  all  the  nitrogen  taken  into  the  system  in  the 
form  of  nitrogenous  food. 

General  properties.  Normal  human  urine,  when  in  a  fresh  state, 
is  a  clear,  transparent  aqueous  liquid,  of  a  lighter  or  deeper  amber 
color,  having  a  peculiar,  faintly  aromatic  odor,  a  bitter,  saline  taste, 
a  distinct  acid  reaction  on  blue  litmus-paper,  and  a  specific  gravity 
heavier  than  water  (average  about  1.020).  When  urine  is  kept  in  a 
clean  vessel  it  may  remain  unchanged  for  several  days,  provided  the 
temperature  be  not  too  high,  and  the  amount  of  total  solid  con- 
stituents not  too  small. 

In  urine,  shortly  after  cooling,  especially  if  it  be  concentrated,  a 
light,  cloudy  film  of  mucus  is  formed,  which  slowly  sinks  to  the 
bottom ;  the  acid  reaction  gradually  increases,  small  yellowish-red 
crystals  of  acid  urates,  or  uric  acid,  are  deposited.  In  this  condition 
the  urine  may  often  continue  unchanged  for  several  weeks,  provided 
the  temperature  be  low.  If,  however,  the  urine  be  very  dilute,  and 
the  temperature  above  the  mean,  decomposition  speedily  takes  place. 
The  urine  is  then  found  to  be  covered  with  a  thin,  shining,  and  fre- 
quently iridescent  membrane,  fragments  of  which  sink  gradually  to 
the  bottom.  The  urine  then  becomes  turbid,  acquires  a  pale  color, 
its  reaction  becomes  alkaline,  and  it  begins  to  develop  a  nauseous 
ammoniacal  odor,  due  to  the  products  formed  by  the  decomposing 
action  of  certain  microorganisms  (chiefly  bacterium  urese  and  micro- 


UEINE  AND  ITS  NORMAL  CONSTITUENTS.  453 

coccus  urese)  upon  urea,  which  is  converted  into  ammonium  carbonate. 
The  change  from  an  acid  to  an  alkaline  urine  causes  the  precipitation 
of  earthy  phosphates,  ammonium-magnesium  phosphate,  ammonium 
urate,  etc. 

Composition.  Urine  is  chiefly  an  aqueous  solution  of  urea  and 
inorganic  salts,  containing,  however,  always  some  uric  acid,  mucus, 
coloring  and  other  organic  matters.  The  average  composition  of 
normal  human  urine  may  be  stated  thus : 

Water .     95.76  per  cent. 

Urea 2.50        " 

Uric  acid 0.04 

Hippuric  acid . 

Kreatin  . 

Kreatinin        .        .         .         ,  0.40  per  cent. 

Coloring  matter 

Mucus     .... 

Unknown  organic  matters 

f  sodium 


Phosphates^  potassium 

Chlorides     [     of     -{   calcium 


Sulphates    -  |   magnesium 

I  iron 


1.30  per  cent. 


The  above  average  composition  of  human  urine  varies  considerably, 
and  is  influenced  by  the  water  and  food  taken,  amount  of  work  done, 
time  of  day,  temperature  of  air,  age,  sex,  etc. 

Urine  also  contains  gaseous  constituents,  amounting  to  about  16 
per  cent,  by  volume  ;  these  gases  are  chiefly  carbon  dioxide  (88  per 
cent.),  and  nitrogen  (11  per  cent.),  with  very  little  oxygen  (1  per 
cent.). 

The  quantity  of  urine  passed  in  a  day  also  varies  widely,  an  adult 
discharging  from  500  to  2300  c.c.  in  twenty-four  hours;  a  normal 
average  quantity  is  about  1400  to  1600  c.c.  (about  49  to  56  ounces). 
The  quantity  of  total  solids  contained  in  this  urine  varies  from  55 
to  60  grammes  (840  to  920  grains),  and  over  one-half  of  this  quantity 
is  urea. 

NH2  .CO 

Urea,    Carbamide,    COH4N2,    or    COil(  or    N2=H2     or 

XNH2  %H2 

CO(NH2)2.  Urea  is  the  most  important  constituent  of  urine,  and  is 
the  substance  which  carries  oif  by  far  the  largest  quantity  of  all 
nitrogen  taken  in  the  food.  Urea  has  never  yet  been  found  as  a 
product  of  vegetable  life,  but  is  found  as  a  normal  constituent  of  the 


454  PHYSIOLOGICAL  CHEMISTRY. 

urine  of  the  mammalia,  and  in  smaller  quantity  in  the  excrement  of 
birds,  fishes,  and  some  reptiles.  It  occurs  also  in  blood,  muscular 
tissue,  chyle,  lymph,  bile,  perspiration,  and  many  other  animal  fluids. 
When  pure,  urea*  crystallizes  from  an  aqueous  solution  in  colorless 
prisms ;  it  is  odorless,  and  has  a  cooling,  bitter  taste ;  it  easily  dis- 
solves in  water,  the  solution  having  a  neutral  reaction  ;  it  fuses  when 
heated  to  130°  C.  (266°  F.),  but  decomposes  at  a  higher  temperature, 
giving  oif  ammonia  gas  and  water,  whilst  a  number  of  other  sub- 
stances are  formed  at  the  same  time.  A  pure  solution  of  urea  does 
not  decompose  at  ordinary  temperature,  but  on  boiling,  and  especially 
under  pressure,  it  takes  up  water,  and  is  decomposed  into  ammonia 
and  carbon  dioxide,  or  into  ammonium  carbonate : 

CO(NH2)2  +  2H2O  =  C02  -f  2NH3  +  H2O  =  (NH4)2CO3. 

The  same  decomposition  takes  place  in  urine  under  the  influence 
of  a  ferment  (most  likely  present  in  urine,  or  perhaps  derived  from 
the  air),  if  the  temperature  be  not  too  low. 

A  solution  of  urea  is  decomposed  by  the  action  of  chlorine  or 
bromine  with  generation  of  hydrochloric  (or  hydrobromic)  acid, 
carbon  dioxide,  and  nitrogen : 

CO(NH2)2  +  6C1  +  H2O  =  6HC1  -f  CO2  +  2N. 

Alkali  hypochlorites  or  hypobromites  cause  a  similar  decomposi- 
tion, upon  which  is  based  the  quantitative  estimation  of  urea. 

Urea  forms  with  acids  definite  salts,  and  with  certain  oxides  and 
salts  definite  compounds. 

Urea  is  formed  artificially  by  numerous  decompositions,  as,  for  instance : 

a.  By  a  process  similar  to  the  one  taking  place  in  the  animal  system,  viz.* 
by  limited  oxidation  of  albuminous  substances  by  potassium  permanganate. 

b.  By  oxidation  of  uric  acid  in  the  presence  of  water : 

C5H4N403  +  HaO  +  O  =  CO(NH8)2  +  C4H2N2O4. 
Uric  acid.  Urea.  Alloxan. 

c.  By  the  action  of  caustic  alkalies  upon  kreatin : 

C4H9N302    +    H2O    =    CO(NH2)2     +     C3H7NO2. 
Kreatin.  Urea.  Sarcosine. 

d.  By  the  molecular  transformation  of  ammonium  cyanate,  which  takes 
place  when  its  solution  is  evaporated  and  allowed  to  crystallize : 

NH4.CNO    :   :    CO(NH2)2. 

e.  By  the  action  of  carbonyl  chloride,  COC12,  on  ammonia : 

COC12     +    2NH3    =    2HC1    +    CO(NH2)2. 
/.  By  the  action  of  ammonia  on  ethyl  carbonate : 

(C2H5)2C03    +    2NH3    =    2(C2H5OH)     -f     CO(NH2)2. 


URINE  AND  ITS  NORMAL  CONSTITUENTS.  455 

Urea  may  be  obtained  from  urine  by  evaporating  it  to  the  consist- 
ence of  a  syrup  and  mixing  the  cooled  residue  with  an  equal  volume 
of  nitric  acid,  when  crystals  of  urea  nitrate,  CO(NH2)2.HNO3,  form, 
which  may  be  decomposed  by  barium  carbonate  into  urea  and  barium 
nitrate : 

2[CO(NH2)2.HN03]  +  BaC03  ==  CO(NH2)2  +  Ba(NO3)2  +  CO2  +  H2O. 

Experiment  69.  Evaporate  about  200  c.c.  of  urine  to  a  syrupy  consistence, 
allow  to  cool,  place  the  vessel  containing  the  syrup  in  ice  and  add  slowly  with 
stirring  a  volume  of  nitric  acid  equal  to  that  of  the  evaporated  urine.  Set 
aside  for  twenty-four  hours,  collect  the  crystalline  mass  of  urea  nitrate  on  a 
filter,  wash  with  very  little  cold  water,  allow  to  drain  well  and  dissolve  in  hot 
water.  (If  much  colored,  shake  the  solution  with  animal  charcoal  and  filter. ) 
To  the  hot  solution  add  freshly  precipitated  barium  carbonate  as  long  as  car- 
bon dioxide  escapes.  Filter  and  evaporate  the  solution  to  dryness  over  a  water- 
bath  ;  boil  the  mass  with  alcohol,  which  dissolves  the  urea,  but  does  not  act  on 
the  barium  nitrate.  Allow  the  urea  to  crystallize  from  the  alcoholic  solution. 

Reactions  and  determination  of  urea.  There  are  no  very 
characteristic  reactions  by  which  urea  can  be  well  recognized.  From 
organic  mixtures  it  is  separated  by  digesting  them  with  from  3  to  4 
volumes  of  alcohol  in  the  cold ;  the  filtered  liquid  is  evaporated  to 
dryness  and  extracted  with  alcohol,  which  again  is  evaporated.  The 
dry  residue  may  be  tested  for  urea  as  follows : 

1.  Dissolved  in  a  few  drops  of  water,  the  addition  of  an  equal 
quantity  of  colorless  nitric  acid  causes  the  formation  of  white,  shining, 
crystalline  plates  or  prisms  of  urea  nitrate. 

2.  If  a  strong  solution  of  oxalic  acid  is  added,  instead  of  nitric 
acid,  rhombic  plates  of  urea  oxalate  form. 

3.  The  residue  (or  urea)  heated  in  a  test-tube  to  about  160°  C. 
(320°  F.)  until  no  more  vapors  of  ammonia  are  evolved,  leaves  a 
substance  termed  biuret,  C2H6N3O2,  which  upon  the  addition  of  a  few 
drops  of  potassium  hydroxide  solution  and  a  drop  of  cupric  sulphate 
solution,  causes  the  solution  of  the  cupric  hydroxide  with  a  reddish- 
violet  color. 

The  quantitative  estimation  of  urea  in  urine  may  be  effected  by  vari- 
ous methods,  of  which  but  one  will  be  mentioned,  because  it  requires 
less  time  and  less  skill  in  manipulation  than  most  other  methods. 
This  determination  is  based  upon  the  fact  that  urea  is  decomposed  by 
alkali  hypobromites  into  carbon  dioxide,  water,  and  nitrogen  : 
CO(NH2)2  +  3(NaBrO)  =  3NaBr  +  CO2  +  2H2O  +  2N. 

The  liberated  nitrogen  is  collected,  and  from  its  volume  its  weight 
and  that  of  the  urea  are  calculated. 


456 


PHYSIOLOGICAL  CHEMISTRY. 


Practically,  the  operation  is  conducted  as  follows  :  100  grammes  of 
sodium  hydroxide  are  dissolved  in  250  c.c.  of  water,  and  to  this 
cooled  solution  are  added  25  c.c.  of  pure  bromine,  when  sodium 
hypobromite  is  formed,  leaving,  however,  an  excess  (over  one-half) 


FIG.  41. 


Apparatus  for  the  volumetric  estimation  of  urea. 

of  the  sodium  hydroxide  in  an  unaltered  condition.  (The  solution 
easily  decomposes,  and  should,  therefore,  be  freshly  prepared  for 
analysis.) 

The  apparatus  required  (Fig.  41)  consists,  in  its  most  simple  form, 
of  a  wide-mouth  bottle,  A;  a  small  test-tube,  B,  of  about  10  c.c. 
capacity;  a  glass  cylinder,  c,  and  a  graduated  burette,  D. 

Into  a  bottle  is  fitted  a  perforated  cork,  which  is  connected  by 
means  of  tubing  with  the  burette.  5  c.c.  of  urine  are  introduced 
into  the  test-tube  and  20  c.c.  of  the  alkali  hypobromite  solution  into 
the  bottle,  care  being  taken  not  to  bring  the  liquids  in  contact  with 
each  other.  The  graduated  burette  is  lowered  in  the  cylinder,  until 
the  zero-mark  is  on  a  level  with  the  surface  of  the  water  in  the 


URINE  AND  ITS  NORMAL  CONSTITUENTS.  457 

cylinder  and  the  connection  between  the  burette  and  the  bottle  made. 
By  now  inclining  the  bottle  so  that  the  urine  comes  in  contact  with 
the  hypobromite,  decomposition  of  urea  takes  place  energetically. 
The  liberated  carbon  dioxide  is  absorbed  by  the  sodium  hydroxide, 
while  the  nitrogen  increases  the  volume  of  air  present  in  the  appa- 
ratus. The  burette  is  gradually  raised  as  the  nitrogen  is  evolved, 
and  the  whole  allowed  to  stand  for  half  an  hour.  The  cubic  centi- 
meters of  nitrogen  gas  are  read  off  (whilst  the  water  in  the  burette 
and  cylinder  are  on  a  level),  and  give,  multiplied  by  0.0027,  the 
grammes  of  urea  in  5  c.c.  of  urine. 

As  the  volume  of  gas  depends  upon  temperature  and  pressure, 
corrections  for  these  have  to  be  made  by  using  the  following  formula : 

_  100  y  b 

P  ~~  760.370.  a  (1  +  0.003665^. 
p  =  Weight  of  urea  for  100  c.c.  urine, 
a  =  Volume  of  urine  used,  expressed  in  c.c. 
v  =  Volume  of  nitrogen  read  off. 
b  =  Barometric  pressure  in  mm. 
t   =  Temperature  during  the  measurement  of  nitrogen. 

370  represents  the  c.c  of  nitrogen  (at  0°  and  760  mm  pressure) 
obtained  from  one  gramme  of  urea. 

The  above  described  process  for  estimation  of  urea  is,  for  various 
reasons,  far  from  being  perfect  (uric  acid  and  kreatin,  for  instance, 
are  also  decomposed  with  liberation  of  nitrogen ;  but  it  has  been 
found  that  the  results  obtained  are  quite  sufficient  for  clinical  purposes. 

Experiment  70.     Determine  urea  in  urine  by  the  method  described  above. 

Uric  acid,  H2C5H2N4O3.  Uric  acid  is  found  in  small  quantities  in 
human  urine,  chiefly  in  combination  with  sodium,  potassium,  and 
ammonium,  but  also  with  calcium  and  magnesium.  In  larger  propor- 
tions, uric  acid  is  found  in  the  excrement  of  birds,  mollusks,  insects, 
and  chiefly  of  serpents,  the  solid  urine  of  the  latter  consisting  almost 
entirely  of  uric  acids  and  urates.  It  is  also  found  in  Peruvian  guano. 

Pure  uric  acid  is  a  white,  crystalline,  tasteless,  and  odorless  sub- 
stance, almost  insoluble  in  water,  requiring  1900  parts  of  boiling  and 
15,000  parts  of  cold  water  for  its  solution  ;  it  is  also  insoluble,  or 
nearly  so,  in  alcohol  and  ether.  The  great  insolubility  of  uric  acid 
causes  its  separation  in  the  solid  state,  both  in  the  bladder  and  in  the 
tissues. 

Reactions  and  determination  of  uric  acid.  Uric  acid  may  be 
recognized  by  its  crystalline  form,  and  by  the  murexid  test,  which  is 


458  PHYSIOLOGICAL  CHEMISTRY. 

made  by  placing  a  fragment  of  uric  acid  in  a  porcelain  dish,  adding 
a  drop  of  nitric  acid,  and  carefully  evaporating  over  a  flame.  To  the 
dry  residue  a  drop  of  ammonia  water  is  added,  which  produces  a 
beautiful  purplish  red  color.  (Plate  VIII.,  4.)  This  reaction  occurs, 
however,  also  with  a  number  of  substances  which  are  similar  to,  but 
more  complex  in  composition  than  uric  acid. 

The  quantitative  estimation  of  uric  acid  in  urine  is  best  accomplished 
by  adding  10  c.c.  of  hydrochloric  acid  to  250  c.c.  of  urine,  setting 
aside  for  24  hours  in  a  cool  place,  and  collecting  the  crystals  of  uric 
acid  on  a  small  filter  which  has  been  previously  weighed.  The 
crystals  are  washed  with  a  little  water,  and  dried  at  100°  C.  (212°  F.). 
As  uric  acid  is  not  entirely  insoluble,  0.0038  gramme  has  to  be  added 
for  every  100  c.c.  of  urine  employed  for  the  analysis. 

If  the  urine  (to  be  tested  for  uric  acid)  be  very  dilute,  it  should  be 
evaporated  to  about  one-half  its  bulk  before  adding  hydrochloric 
acid ;  if  it  contain  albumin,  this  should  be  removed  by  adding  a  drop 
of  acetic  acid,  boiling  and  filtering. 

Hippuric  acid,  C9H9NO3  (Benzyl-glycocol,  Benzyl-amido-acetic  acid), 
is  a  normal  constituent  of  human  urine,  but  is  found  in  much  larger 
quantities  in  the  urine  of  herbivora.  Its  constitution  may  be  con- 
sidered as  ammonia  in  which  two  hydrogen  atoms  are  replaced  by  the 

/C7H50 
radicals  of  benzoic  and  acetic  acid  respectively,  thus,  N_ C2H3O2. 

\H 

Hay,  and  especially  aromatic  herbs,  contain  benzoic  acid,  or  com- 
pounds having  a  similar  composition,  and  a  portion  of  these  com- 
pounds is  eliminated  in  hippuric  acid.  Administration  of  benzoic 
acid  increases  the  amount  of  hippuric  acid  in  urine. 

When  pure,  hippuric  acid  crystallizes  in  transparent,  colorless, 
odorless  prisms,  which  have  a  bitter  taste,  and  are  sparingly  soluble 
in  water. 

Analytically,  hippuric  acid  is  characterized — 

1.  By  giving  a  sublimate  of  benzoic  acid,  and  an  odor  of  hydro- 
cyanic acid,  when  heated  in  a  dry  test-tube. 

2.  By  giving  a  brown  precipitate  with  ferric  chloride. 

3.  By  giving  off  benzene  and  ammonia  when  heated  with  calcium 
hydroxide. 

4.  By  evolving  an  intense  odor  of  nitro-benzene  when  evaporated 
to  dryness  with  a  few  drops  of  nitric  acid. 

Other  organic  substances,  such  as  kreatin,  kreatinin,  xanthin,  lactic 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       459 

acid,  mucus,  coloring  matters,  etc.,  occur  in  such  small  quantities  in 
normal  urine  that  their  detection,  separation,  and  quantitative  estima- 
tion are  very  difficult,  and  are  almost  exclusively  attempted  during 
scientific  investigations. 


56.   EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE. 

Points  to  be  considered  in  the  analysis  of  urine.     They  are : 

1.  Color,  odor,  general  appearance — whether  clear,  smoky,  cloudy, 
turbid,  etc. 

2.  Reaction — whether  acid,  neutral,  or  alkaline  to  test-paper. 

3.  Specific  gravity. 

4.  Total  amount  of  organic  and  inorganic  solids. 

5.  Total  amount  of  inorganic  matter  (ash). 

6.  Determination  of  urea. 

7.  Determination  of  uric  acid. 

8.  Determination  of  inorganic  acids  and  bases.     (Hydrochloric, 
sulphuric,  and  phosphoric  acids;  sodium,  potassium,  calcium,  mag-, 
nesiurn,  and  iron.) 

9.  Determination  of  albumin. 

10.  Determination  of  sugar. 

11.  Examination  for  bile. 

12.  Examination  of  any  organic  or  inorganic  sediment,  either  by 
chemical  means  or  by  the  microscope. 

Samples  of  urine  should  always  be  drawn  from  the  well-mixed  and 
exactly  measured  quantity  of  the  total  urine  discharged  in  twenty- 
four  hours. 

Color.  Normal  urine  is  generally  pale-yellow  or  reddish-yellow, 
but  it  may  be  as  colorless  as  water,  or  as  dark  brownish-black  as 


QUESTIONS. — 541.  What  is  urine,  where  and  by  what  process  is  it  formed  in 
the  animal  body,  and  what  is  its  function?  542.  Mention  the  general  physi- 
cal and  chemical  properties  of  urine.  543.  Give  the  average  composition  of 
human  urine,  and  state  by  what  conditions  the  composition  is  influenced.  544. 
State  the  composition  and  properties  of  urea.  545.  By  what  process  is  urea 
formed  in  the  animal  body,  and  how  can  it  be  obtained  artificially?  546. 
Describe  a  process  by  which  urea  may  be  estimated  quantitatively  in  urine. 

547.  In  what  forms  is  uric  acid  found  in  urine,  and  what  are  its  properties  ? 

548.  Describe  the  murexid  test.       549.  How  can  uric  acid  be  determined 
quantitatively  in  urine  ?     550.  What  is  hippuric  acid,  and  by  what  tests  may 
it  be  recognized  ? 


460  PHYSIOLOGICAL  CHEMISTRY. 

porter ;  a  reddish  and  smoky  tint  generally  indicates  the  presence  of 
blood,  and  a  brownish-green  suggests  the  presence  of  the  coloring 
matter  of  bile.  (Plate  VIII.,  1-3.) 

The  true  nature  of  the  normal  coloring  matters  of  urine  is  as  yet 
doubtful ;  the  existence  of  at  least  two  has,  however,  been  demon- 
strated ;  they  have  been  named  urobilin  and  urochrome,  and  are,  most 
likely,  products  of  the  decomposition  of  biliary  matters. 

Abnormal  coloring  matters  are  chiefly  those  of  blood,  bile,  and  of 
certain  vegetables ;  thus,  rhubarb  and  senna  leaves  cause  a  reddish- 
yellow  to  deep  red  color,  especially  in  alkaline  urine;  santonin  pro- 
duces a  bright-yellow  color,  changing  to  red  or  crimson  on  the 
addition  of  an  alkali.  Carbolic  acid  introduced  into  the  system 
causes  a  dark,  or  even  black  discoloration  of  urine,  while  large  doses 
of  salicylic  acid  color  it  green. 

The  coloring  matters  of  blood  may  be  recognized  by  adding  to  a  few 
drops  of  urine  a  drop  of  freshly  prepared  tincture  of  guaiacum,  and 
agitating  with  a  solution  of  ozonized  ether  (ethereal  solution  of  hydro- 
gen dioxide) ;  the  latter  is  colored  blue  in  case  haemoglobin  is  present. 
In  place  of  ozonized  ether,  oil  of  turpentine  which  has  been  in  contact 
with  atmospheric  air  for  some  weeks  may  be  used,  and  the  test  made 
by  allowing  urine  to  flow  down  the  test-tube  containing  a  mixture  of 
the  oil  and  tincture  ;  a  blue  coloration  will  slowly  appear,  if  blood 
be  present.  The  test  has  the  serious  disadvantage  that  protoplasm  in 
almost  any  form  will  give  the  blue  color. 

Detection  of  biliary  coloring  matter  will  be  considered  later. 

Indican,  C8H6N.HSO4.  This  substance  is  pale-yellow,  but  yields 
readily  blue  indigo  by  oxidation.  It  occurs  in  very  small  quantities 
in  normal  urine,  but  is  much  increased  in  cases  of  marked  intestinal 
fermentation,  also  in  abdominal  diseases,  in  peritonitis,  and  especially 
in  obstructions  of  the  bowel. 

Indican  is  recognized  as  follows :  Equal  volumes  of  strong  hydro- 
chloric (or  nitric)  acid  and  urine  are  mixed  in  a  test-tube,  and,  drop 
by  drop,  while  shaking  the  tube,  a  freshly-prepared  1  per  cent,  solu- 
tion of  bleaching  powder  is  added.  Normal  urine  shows  a  green 
color  only,  while  large  quantities  of  indican  are  indicated  by  a  more 
or  less  distinct  blue  color.  By  shaking  the  contents  of  the  test-tube 
with  a  little  chloroform,  indican  is  dissolved  by  the  latter,  imparting 
to  it  a  blue  color. 

Indigo-red  appears  in  the  urine  in  the  same  conditions  in  which 
indican  is  found.  It  is  recognized  by  Rosenbach's  reaction  :  Urine 
is  boiled,  and  while  it  is  still  boiling  nitric  acid  is  added  drop  by 


vm. 


URINE. 


Urine  tints— Pale  yellow,  light  yel- 
low, yellow. 


Urine  tints— Reddish  yellow,  yel- 
lowish red, red. 


Urine  tints— Brownish   red,    red- 
dish brown,  brownish  black. 


Murexitl  test  for  uric  acid. 


Trommer's  orPenling's  test  for 
sugar. 


Bbtger's  bismuth  test  for  sugar. 


Omeliii's  test  for  biliary  coloring 
matters. 


Pettenkofer's     test    for    biliary 
acids. 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.      461 

drop,  when  a  deep-red  color  appears,  if  indigo-red  is  present.     The 
foam  on  shaking  the  test-tube  is  bluish-red. 

Odor.  The  normal  odor  of  fresh  urine  is  characteristic,  and  is 
sometimes  spoken  of  as  aromatic;  it  is  not  known  by  what  substance 
or  substances  this  odor  is  caused.  The  ammoniacal  and  putrescent 
odor  which  urine  acquires  on  standing  is  due  to  the  products  of  de- 
composition formed,  chiefly  ammonia. 

A  number  of  substances  taken  internally  and  separated  by  the  kidneys  from 
the  blood,  cause  the  urine  to  assume  a  characteristic  odor ;  aromatic  substances 
especially  impart  such  odors;  oil  of  turpentine  gives  an  odor  reminding  of 
violets,  and  the  odor  of  cubebs,  copaiba,  asparagus,  garlic,  valerian,  and  other 
substances  is  promptly  transferred  to  the  urine  of  persons  using  these  drugs 
internally.  A  sweetish  smell  sometimes  attends  the  presence  of  large  quantities 
of  sugar  in  urine. 

Reaction.  This  is  generally  acid  in  healthy  urine  which  has  been 
recently  passed,  but  may  become  neutral  or  alkaline  within  a  short 
period,  by  decomposition  of  urea  and  formation  of  ammonium  car- 
bonate. The  acid  reaction  of  urine  is  due  chiefly  to  monosodium 
ortho-phosphate,  NaH2PO4,  and  perhaps  also  to  the  acid  salts  of 
uric  acid. 

The  acidity  may  be  determined  volumetrically  by  the  addition  of  deci-normal 
solution  of  sodium  or  potassium  hydroxide  to  100  c.c.  of  urine,  using  litmus- 
paper  as  an  indicator.  The  acidity  of  urine  is  generally  expressed  as  oxalic 
acid,  of  which  1  c.c.  of  normal  potash  solution  neutralizes  0.0063  gramme.  If, 
for  instance,  100  c.c.  of  urine  require  15  c.c.  of  deci-normal  potash  solution, 
then  the  acidity  of  the  100  c.c.  urine  is  15  X  0.0063  =  0.0945 ;  and  for  the  total 
urine  of  the  24  hours — say  1800  c.c. — the  acidity  expressed  as  oxalic  acid  is, 
therefore,  equal  to  1.701  grammes. 

While  urine  shows  an  acid  reaction  generally,  it  may  have  a  neutral 
or  even  alkaline  reaction.  In  many  cases  this  alkaline  reaction  points 
to  decomposition  of  urea  in  the  bladder,  but  it  may  be  due  also  to  the 
elimination  of  alkali  carbonates,  derived  from  food  taken  or  drugs 
administered. 

Thus,  the  alkali  tartrates,  citrates,  acetates,  etc.,  have  (after  diges- 
tion) a  tendency  to  neutralize  uric  acid,  and  an  excess  of  them  is 
eliminated  as  carbonate. 

To  distinguish  between  the  harmless  alkaline  reaction  caused  by 
fixed  alkalies  and  the  alkaline  reaction  produced  by  decomposition  of 
urea,  a  piece  of  red  litmus-paper  may  be  used.  If  this,  after  having 
been  moistened  with  the  urine,  remains  blue  on  drying  (by  warming 


462 


PHYSIOLOGICAL  CHEMISTRY. 


gently)  the  reaction  is  due  to  the  fixed  alkalies;  if  the  red  color  reap- 
pears, the  alkaline  effect  is  due  to  ammonia  compounds. 

Urine  sometimes  is  amphoteric  in  its  reaction,  i.  e.,  it  colors  red  litmus-paper 
faintly  blue,  and  blue  litmus-paper  slightly  red.     This  condition  is  caused 

most  likely  by  the  simultaneous  presence  of 
FIG.  42.  monosodium  orthophosphate,  NaH2P04,  which 

has  an  acid,  and  of  disodium  orthophosphate, 
^,  which  has  an  alkaline  reaction. 


Experiment  71.  Prepare  normal  soda  solu- 
tion as  directed  on  page  258,  dilute  it  with  9 
parts  of  water,  and  titrate  with  this  deci-  nor- 
mal solution  100  c.c.  of  urine,  using  litmus- 
paper  as  an  indicator. 

Specific  gravity.  The  normal  spe- 
cific gravity  of  an  average  amount  of 
1500  c.c.  of  urine  passed  in  twenty-four 
hours  is  about  1.020,  but  it  varies,  even 
in  health,  from  1.012  to  1.030  or  more. 
A  specific  gravity  above  1.030  may  in- 
dicate the  presence  of  sugar,  larger 
quantities  of  which  may  cause  the  spe- 
cific gravity  to  rise  to  1.050.  Albu- 
minous urine  is  frequently  of  low 
specific  gravity,  1.010  to  1.012. 

It  should  be  remembered  that  the 
specific  gravity  of  urine  considered  sep- 
arately from  the  quantity  of  urine  passed 
in  twenty-four  hours  is  of  no  value,  and 
that  in  some  diseases  (for  instance  in 
acute  nephritis  with  albuminuria)  the 
specific  gravity  of  albuminous  urine 
may  be  as  high  as  1  .030,  while  a  diabetic 

urine  may  have  a  specific  gravity  of  1.025,  or  less,  in  consequence  of 

a  large  volume  passed. 

The  determination  of  the  specific  gravity  of  urine  is  generally 

accomplished  by  the  urinometer,  which  is  a  small  hydrometer  indicat- 

ing specific  gravity  from  zero  (or  1000)  to  60  (or  1060).     (See  Fig. 

42.)     As  the  temperature  influences  the  density  of  liquids,  a  urin- 

ometer  can  only  give  correct  results  at  a  certain  degree  of  temperature, 

which  is  generally  marked  upon  the  instrument. 


Urinometer. 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       463 

Determination  of  total  solids.  An  approximate  determination 
of  total  solids  may  be  deduced  from  the  specific  gravity  of  the  urine, 
as  it  has  been  found  that  the  last  two  figures  of  the  specific  gravity  of 
urine,  multiplied  by  2.33,  correspond  to  the  number  of  grammes  in 
1000  c.c.  of  urine.  If,  for  instance,  1450  c.c.  of  urine,  of  a  specific 
gravity  of  1.018,  have  been  discharged  in  twenty-four  hours,  then 
the  quantity  of  total  solids  in  1000  c.c.  will  be  18  X  2.33,  or  41.94 
grammes  ;  and  in  1450  c.c.  60.81  grammes. 

A  more  exact  method  of  determining  the  total  solids  in  urine  is  the  evapora- 
tion of  about  10  c.c.  in  a  weighed  platinum  dish  over  a  water-bath  (or,  better^ 
under  the  receiver  of  an  air-pump  over  sulphuric  acid),  until  it  is  found  that 
no  more  loss  in  weight  ensues  on  continued  exposure  of  the  dish  in  the  drying 
apparatus.  By  now  reweighing  the  dish,  plus  contents,  and  deducting  from  the 
weight  that  of  the  empty  dish,  the  weight  of  total  solids  is  found. 

Determination  of  inorganic  constituents.  The  platinum  dish 
containing  the  known  quantity  of  total  solids  is  exposed  to  the  action 
of  a  non-luminous  flame,  and  the  heat  continued  until  all  organic 
matter  has  been  destroyed  and  expelled.  By  reweighing  now,  and 
deducting  the  weight  of  the  platinum  dish,  plus  ash,  from  the  weight 
of  the  dish,  plus  total  solids,  the  quantity  of  total  organic  matter  is 
determined ;  and  by  deducting  weight  of  dish  from  weight  of  dish 
plus  ash,  the  total  quantity  of  inorganic  matter  is  found. 

Experiment  72.  Determine  total  solids,  water,  total  organic  and  inorganic 
matters  in  a  specimen  of  urine  by  following  the  directions  given  above.  Use 
10  or  20  c.c.  of  urine  for  the  analysis. 

The  analysis  of  the  ash  is  effected  by  the  methods  given  in  con- 
nection with  the  consideration  of  the  various  acid  and  basic  constitu- 
ents themselves.  Chlorine  is  determined  by  precipitating  the  solution 
of  the  ash  in  nitric  acid  with  silver  nitrate,  sulphuric  acid  by  barium 
chloride,  phosphoric  acid  by  ammonium  molybdate,  calcium  by  ammo- 
nium oxalate,  potassium  by  platinic  chloride,  iron  by  potassium  ferro- 
cyanide,  etc. 

For  the  determination  of  many  of  the  inorganic  constituents,  it  is 
not  necessary  to  destroy  the  organic  matter  as  described  above,  but 
this  determination  can  be  effected  directly.  Thus,  chlorine  may  be 
precipitated  directly  from  urine  (slightly  acidulated  with  nitric  acid) 
by  silver  nitrate ;  the  precipitated  silver  chloride  is  collected  upon  a 
small  filter,  well  washed,  dried,  and  weighed  in  a  porcelain  crucible, 
after  the  filter  (to  which  particles  of  silver  chloride  adhere)  has  been 


464  PHYSIOLOGICAL  CHEMISTRY. 

burned  separately  and  its  ash  added  to  the  contents  of  the  crucible, 
which  is  moderately  heated  before  weighing. 

Experiment  73.  Determine  the  amount  of  sodium  chloride  solution  volu- 
metrically  by  means  of  potassium  sulphocyanate  as  follows:  Place  5.837 
grammes  (about  5.7  c.c.)  of  urine  into  a  150  c.c.  flask,  add  2  c.c.  of  nitric  acid, 
20  c.c.  of  water,  and  15  c.c.  of  deci-normal  silver  nitrate  solution.  Mix  well, 
add  some  ferric  alum  solution,  and  then  from  a  burette  deci-normal  potassium 
sulphocyanate  solution  until,  after  frequent  shaking  of  the  flask,  the  white  pre- 
cipitate coheres  in  curdy  masses,  and  the  liquid  assumes  a  red  tint.  The 
number  of  c.c.  of  sulphocyanate  required  is  then  deducted  from  the  15  c.c.  of 
silver  nitrate  added  at  first,  and  the  difference  shows  the  number  of  c.c.  of  silver 
nitrate  required  to  precipitate  the  sodium  chloride  in  the  urine.  Normal  urine 
requires  from  8  to  11  c.c.  silver  solution,  each  c.c.  corresponding  to  0.1  per 
cent,  of  sodium  chloride.  (For  explanation  of  the  method  see  page  269.) 

Phosphorie  acid  is  found  in  urine,  in  part  (about  two-thirds)  com- 
bined with  alkalies,  and  in  part  (about  one-third)  with  lime  and 
magnesia.  These  phosphates  have  in  acid  or  neutral  urine  the  com- 
position ]STaH2PO4,  Na2HPO4,  CaHPO4,  CaH4(PO4)2,  MgHPO4 ;  in 
alkaline  urine  compounds  of  the  composition  Na3PO4,  Ca3(PO4)2, 
Mg3(PO4)2,  MgNH4PO4  may  be  present. 

By  adding  any  alkali  the  phosphates  of  calcium  and  magnesium 
(generally  termed  earthy  phosphates)  are  precipitated,  the  phosphates 
of  sodium  or  possibly  potassium  remain  dissolved. 

The  so-called  earthy  phosphates  (phosphates  of  calcium  and  magne- 
sium) may  be  approximately  determined  by  adding  a  few  drops  of  an 
alkaline  hydroxide  to  about  50  c.c.  of  urine,  heating  to  the  boiling- 
point,  collecting  on  a  filter,  washing,  igniting,  and  weighing  in  a 
platinum  crucible. 

Experiment  74.  Add  to  50  c.c.  of  urine  a  few  drops  of  calcium  chloride  solu- 
tion and  then  water  of  ammonia.  Phosphoric  acid  is  completely  precipitated, 
chiefly  as  tricalcium  phosphate,  Ca8(PO4)2,  containing,  however,  a  very  small 
quantity  of  magnesium  ammonium  phosphate.  Collect  the  precipitate  on  a 
filter,  wash  well,  dry,  ignite  and  weigh  it.  Calculate  the  phosphoric  acid  from 
the  tricalcium  phosphate,  without  reference  to  the  small  amount  of  magnesium 
phosphate. 

Experiment  75.  Add  to  100  c.c.  clear  urine  5  c.c.  hydrochloric  acid ;  boil, 
and  then  add  barium  chloride  to  complete  precipitation.  Set  aside  for  one 
hour,  filter,  wash  well,  dry,  ignite  and  weigh.  Calculate  from  the  weight  of 
barium  sulphate,  thus  obtained,  the  percentage  of  sulphuric  acid  present  in  the 
urine  examined. 

The  methods  for  estimating  urea  and  uric  acid  have  been  described 
in  the  preceding  chapter. 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       465 

Detection  of  albumin.  Serum-albumin  and  serum-globulin  are 
the  forms  most  frequently  present  in  urine,  but  peptones  and  other 
albuminoids  are  also  met  with.  The  different  methods  by  which  the 
presence  of  albumin  in  urine  is  demonstrated  are  based  upon  the 
coagulation  of  albumin.  This  coagulation  may  be  accomplished  by 
heat,  by  nitric  acid,  by  picric  acid,  by  potassium  ferrocyanide  in  the 
presence  of  acetic  acid,  and  also  by  either  metaphosphoric  or  tri- 
chloracetic  acid. 

The  urine  used  for  any  of  these  tests  must  be  perfectly  clear;  if  it 
be  not  clear,  it  must  be  rendered  so  by  processes  which  vary  accord- 
ing to  the  nature  of  the  substance  causing  the  turbidity.  In  most 
cases  filtration  through  good  filter-paper  may  be  sufficient ;  but  if  this 
does  not  accomplish  the  desired  result,  it  may  become  necessary  to 
use  other  means.  Thus,  if  earthy,  amorphous  phosphates  be  present 
(which,  especially  in  alkaline  urine,  are  apt  to  pass  through  the  best 
filter-paper),  they  may  be  removed  by  adding  to  the  urine  about  a 
fourth  part  of  potassium  hydroxide  solution,  warming  the  mixture, 
and  filtering.  If  the  turbidity  be  caused  by  urates,  the  urine  will 
generally  become  clear  by  passing  the  test-tube  once  or  twice  through 
a  flame. 

The  clear  urine  is  then  tested  by  either  (or  all)  of  the  following 
methods : 

a.  Coagulation  by  heat.  A  test-tube  is  filled  about  one-half  with 
the  urine,  to  which,  if  not  distinctly  acid  to  test-paper,  a  few  drops 
of  acetic  acid  are  added.1  (In  case  potassium  hydroxide  has  been 
added  in  order  to  precipitate  the  phosphates,  enough  of  acetic  acid 
must  be  added  to  cause  a  distinct  acid  reaction.)  The  test-tube  is  then 
held  over  the  flame  in  such  a  manner  that  the  heat  acts  upon  the  upper 
half  of  the  urine  only,  heating  this  portion  gradually  to  near  the  boil- 
ing point.  By  thus  operating,  two  strata  of  fluid  are  obtained  for 
comparison,  and  by  holding  the  test-tube  against  the  light,  or  against 
a  black  background,  any  difference  in  the  appearance  of  the  upper 
and  lower  strata  may  be  noticed.  Any  cloudiness  or  opacity  seen 
may  be  due  to  albumin,  but  may  also  be  caused  by  earthy  phosphates, 
because  these  are  often  precipitated  by  heating,  and  have  been  mis- 
taken for  albumin  quite  frequently. 

The  reason  why  phosphates  are  often  precipitated  by  heating  of  urine  is  this : 
Urine,  showing  a  slightly  acid  or  neutral  reaction,  contains  dicalcium  and  di- 

1  If  acetic  acid  alone  causes  a  precipitate,  this  may  be  due  to  mucin,  which  should  be  filtered 
Off  before  heating. 

30 


466  PHYSIOLOGICAL  CHEMISTRY. 

magnesium  phosphates,  which  salts  upon  heating  are  decomposed  into  soluble 
monophosphates  and  insoluble  triphosphates,  thus : 

4CaHP04    :   :    Ca(H2P04)2     +     Ca3(PO4)2 
Dicalcium  Monocalcium  Tricalcium 

phosphate.  phosphate.  phosphate. 

To  decide  the  nature  of  the  precipitate  a  few  drops  (10  to  15)  of 
nitric  acid  are  allowed  to  flow  gently  down  the  side  of  the  tube  into 
the  urine.  The  precipitate  will  readily  disappear  when  caused  by 
phosphates,  but  will  be  permanent  when  albumin  is  present. 

Instead  of  heating,  as  above  described,  merely  the  upper  half  of  the 
urine,  the  total  quantity  of  the  urine  (acidulated  by  a  few  drops  of 
acetic  acid)  may  be  heated,  and  the  test-tube  set  aside  for  several  hours 
(after  having  added  10  to  15  drops  of  nitric  acid),  in  order  to  allow 
the  albumin  to  subside,  when  it  can  be  more  distinctly  seen  and  its 
quantity  noticed. 

b.  Nitric  acid  test.     A  test-tube  is  filled  to  the  depth  of  about  half 
an  inch  with  colorless  nitric  acid,  and  an  equal  quantity  of  urine  is 
allowed  to  flow  down  the  side  of  the  test-tube  in  such  a  manner  that 
the  specifically  lighter  urine  forms  a  distinct  and  separate  layer  over 
the  nitric  acid.     (If  the  urine  be  allowed  to  flow  from  a  pipette,  as 
shown  in  Fig.  43,  the  formation  of  the  two  strata  is  easily  accom- 
plished.)    In  case  albumin  is  present,  a  white  band  or  zone  of  vary- 
ing thickness  (according  to  the  quantity  of  albumin  present)  appears 
at  the  point  of  contact. 

If  the  urine  be  highly  concentrated,  a  similar  white  zone  is  formed 
between  the  acid  and  urine,  due  to  the  separation  of  insoluble  acid 
urates ;  the  difference  between  the  separated  u rates  and  albumin  is 
that  the  latter  forms  a  sharply  defined  zone,  whilst  the  urates  diffuse 
into  the  urine  above.  Moreover,  the  urates  dissolve  on  the  applica- 
tion of  heat.  Finally,  the  separation  of  acid  urates  may  be  avoided 
by  diluting  the  urine  with  an  equal  volume  of  water  and  placing  this 
diluted  urine  upon  the  nitric  acid. 

c.  Picric  acid  test  for  albumin.     This  test  has  the  advantage  that 
neither  phosphates  nor  urates  can  be  mistaken  for  albumin.     It  con- 
sists in  slowly  dropping  urine  into  a  test-tube  filled  to  about  one- 
fourth  with  a  highly  colored  solution  of  picric  acid  in  water.     In  the 
presence  of  albumin  a  white  cloud  or  sharply  defined  white  turbidity 
is  formed,  and  on  warming  the  liquid  the  albumin  collects  into  balls 
which  rise  to  the  surface  of  the  liquid. 

d.  Potassium  ferrocyanide  test.     5  to  10  c.c.  of  cold  urine  are  acidu- 
lated with  5  to  10  drops  of  acetic  acid,  and  to  the  mixture  are  added 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       467 

a  few  drops  of  solution  of  potassium  ferrocyanide.  In  the  presence  of 
even  traces  of  albumin  a  turbidity  is  caused.  This  test  is  extremely 
delicate,  especially  when  modified  so  as  to  allow  a  few  c.c.  of  diluted 
acetic  acid,  to  which  a  few  drops  of  potassium  ferrocyanide  solution 
had  been  added,  to  flow  down  the  side  of  the  test-tube  containing  the 
urine.  A  decided  turbidity  at  the  point  of  contact  of  the  two  liquids 
shows  albumin. 

FIG.  43. 


Nitric  acid  test  for  urine. 

In  case  the  addition  of  acetic  acid  to  the  cold  urine  should  cause  a 
turbidity  (which  may  be  due  to  mucin)  it  must  be  filtered  before  add- 
ing the  potassium  ferrocyanide. 

e.  Metaphosphorie  acid  (glacial  phosphoric  acid)  or  trichlor-acetic 
acid  may  be  used  for  the  detection  of  albumin  by  dropping  a  fragment 
of  either  substance  into  a  few  c.c.  of  urine  contained  in  a  test-tube. 
As  the  acids  dissolve,  a  cloudy  ring  forms  in  the  presence  of  albumin, 
which  is  not  dissolved  on  warming. 

/.  Tanret's  test  is  made  by  means  of  a  solution  containing  of  potassium  iodide 
3  32  grammes,  mercuric  chloride  1.35  grammes,  acetic  acid  20  c.c.  in  a  sufficient 
amount  of  water  to  make  100  c.c.  For  Millard's  test  is  required  a  solution  made 
by  mixing  2  parts  of  carbolic  acid  with  7  parts  of  glacial  acetic  acid  and  22 
parts  of  potassium  hydroxide  solution.  Both  solutions  give  on  heating  pre- 
cipitates with  albumin,  even  when  present  in  very  small  quantity. 

In  the  above  methods  the  manipulations  and  precautions  are  min- 
utely described,  in  order  to  detect  small  quantities  or  even  traces  of 
albumin.  When  albumin  is  abundantly  present,  there  is  no  difficulty 


468  PHYSIOLOGICAL  CHEMISTRY. 

whatever  in  its  detection,  as  heat  will  precipitate  it  from  an  acid, 
neutral,  or  sometimes  even  alkaline  urine ;  the  precipitate  should, 
however,  always  be  tested  by  the  addition  of  a  few  drops  of  nitric 
acid,  and  the  previous  addition  of  a  few  drops  of  acetic  acid  is  also 
advisable. 

A  neutral  urine  should  never  be  acidified  by  nitric  acid  (instead  of 
acetic  acid),  because  a  drop  or  two  of  nitric  acid  may  in  some  cases 
prevent  the  coagulation  of  albumin  by  heat,  though  a  larger  quantity 
(10  to  20  drops)  has  no  such  effect. 

Quantitative  estimation  of  albumin.  The  average  amount  of 
albumin  present  in  acute  cases  of  albuminuria  is  0.1  to  0.5  per  cent., 
rarely  over  1  per  cent.,  though  it  may  rise  to  4  per  cent.  An 
approximate  method  for  the  comparative  estimation  of  albumin  is  to 
precipitate  it  (with  the  precautions  above  given)  in  a  graduated  test- 
tube  by  heat  and  setting  aside  for  twelve  (or  better  for  twenty-four) 
hours.  At  the  end  of  that  time  the  proportion  of  the  coagulated 
albumin  which  has  collected  at  the  bottom  of  the  fluid  is  noticed.  If 
the  albumin  occupy  one-fourth,  one-sixth,  one-tenth  of  the  height  of 
the  liquid,  there  is  said  to  be  one-fourth,  one- sixth,  or  one-tenth  of 
albumin  in  the  urine.  If,  however,  at  the  end  of  twelve  or  twenty- 
four  hours  scarcely  any  albumin  has  collected  at  the  bottom,  there  is 
said  to  be  a  trace. 

The  volumes  of  coagulated  albumin  indicate  the  following  quantities  of  dry 
albumin : 

Slight  turbidity  indicates  about 0.01  per  cent. 

sV  of  the  tube  is  filled 0.05        " 

TV        «•••«•        ...  ...   o.io 

\  "          " 0.25  " 

J  "  0.50 

£  "          " 1.00  " 

Complete  coagulation  .        .        .         .         .  2  to  3  " 

A  better  method  of  exactly  estimating  the  amount  of  albumin  is 
its  complete  separation  and  weighing,  as  described  below. 

Experiment  76.  Acidify  100  c.c.  of  clear  albuminous  urine  with  acetic  acid  ; 
heat  to  the  boiling-point  in  a,  water-bath  for  half  an  hour,  and  filter  through  a 
small  filter,  previously  dried  at  110°  C.  (230°  F.)  and  weighed;  wash  with  boil- 
ing water  to  which  a  little  ammonia  water  has  been  added  (to  remove  uric  acid 
and  urates),  then  with  pure  water  until  the  filtrate  is  not  rendered  turbid  any 
longer  by  silver  nitrate,  next  with  pure  alcohol,  and  finally  with  ether.  Dry 
and  filter  contents  at  110°  C.  (230°  F.)  and  weigh. 

As  it  may  happen  that  the  precipitated  albumin  encloses  earthy  phosphates, 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.      469 

it  is  well  to  burn  filter  with  contents  in  a  platinum  crucible,  and  to  deduct  the 
weight  of  the  remaining  inorganic  residue  (less  the  weight  of  the  filter  ash) 
from  that  of  the  albumin. 

Peptones  may  be  recognized  by  first  precipitating  all  albumin  by 
means  of  boiling  the  urine  acidified  by  acetic  acid,  filtering,  and 
adding  to  the* filtrate  a  few  drops  of  dilute  cupric  sulphate  solution 
and  sodium  hydroxide.  Peptones  will  be  indicated  by  the  purple 
color  of  the  biuret  reaction. 

Blood.  The  presence  of  blood  in  urine  manifests  itself  generally, 
unless  the  amount  be  too  slight,  by  a  blood-red  or  brownish  color 
with  a  bluish,  smoky,  or  greenish  tint,  and  deposits  a  red  or  reddish- 
brown  sediment  after  standing.  As  a  general  rule,  all  constituents 
of  blood,  including  the  corpuscles,  are  present,  but  in  some  cases 
haemoglobin  alone  has  been  found. 

The  tests  for  blood  depend  either  on  the  microscope  or  on  chemical 
changes.  By  the  microscope  is  examined  the  deposit  which  forms  on 
standing ;  almost  unaltered  blood  corpuscles  may  be  found,  or  they 
may  be  much  swollen,  decolorized,  and  deformed  ;  the  corpuscles  are 
generally  accompanied  by  blood  and  fibrin  casts. 

Whenever  blood  is  present,  there  are  necessarily  also  albuminoids, 
which  are  precipitated  by  acidulating  with  acetic  acid  and  boiling, 
when  a  brownish  coagulum  of  albumin  and  hsematin  are  precipitated. 

Haemoglobin  is  also  tested  for  by  means  of  adding  to  the  urine  a 
few  drops  of  freshly  prepared  tincture  of  guaiacum,  a  little  ozonized 
ether,  and  shaking  well.  If  haemoglobin  is  present,  the  ether 
assumes  a  blue  color. 

Detection  of  sugar.  The  sugar  found  in  urine  is  almost  ex- 
clusively glucose,  C6H12O6.  Traces  of  sugar,  or  as  much  as  0.01  per 
cent.,  are  said  to  occur  normally  in  urine,  and  are  of  no  significance ; 
moreover,  it  is  as  yet  doubtful  whether  these  traces  of  sugar  are 
actually  present  in  normal  urine.  A  large  amount  of  sugar  is  often 
indicated  by  a  high  specific  gravity  of  the  urine,  which  then  varies 
from  1.030  to  1.050 ;  the  quantities  found  vary  from  mere  traces  to 
10  per  cent.,  the  latter  quantity,  however,  being  a  very  rare  occur- 
rence, while  3  to  5  per  cent,  is  often  found  in  the  urine  of  persons 
suffering  from  diabetes  mellitus. 

There  are  many  tests  by  which  sugar  can  be  detected.  They 
depend  chiefly  on  the  following  properties  of  sugar,  viz. :  1,  to  act 
as  a  deoxidizing  or  reducing  agent  upon  certain  metallic  oxides 


470  PHYSIOLOGICAL  CHEMISTRY. 

(copper,  bismuth,  silver,  mercury)  in  the  presence  of  alkalies ;  2,  to 
produce  a  yellow  or  brown  color,  when  in  contact  with  alkalies, 
slowly  in  the  cold,  rapidly  on  heating ;  3,  to  give  a  deep  red  color 
with  picrates  in  alkaline  solution,  and  a  number  of  different  colors 
with  certain  phenols  in  the  presence  of  sulphuric  acid  ;  4,  to  ferment 
with  yeast ;  5,  to  unite  with  phenyl-hydrazine  to  a  crystalline  com- 
pound ;  6,  to  have  the  power  of  rotation  to  the  right  of  the  plane  of 
polarization. 

The  tests  for  sugar  should  always  be  preceded  by  tests  for  albu- 
min, which  latter,  if  present,  should  be  removed  by  coagulation  and 
filtration.  Earthy  phosphates  also  interfere  with  the  copper  tests 
sometimes,  because  they  are  precipitated  by  the  alkali,  and  this 
precipitate  may  be  mistaken  either  for  precipitated  cuprous  oxide, 
when  no  sugar  is  present,  or  it  may  cover  the  precipitated  cuprous 
oxide  to  such  an  extent  that  this  is  not  recognized,  when  sugar  is 
present. 

To  avoid  these  errors,  it  is  well  to  render  slightly  alkaline  the 
urine  by  a  few  drops  of  potash  solution,  filter  after  a  few  minutes, 
and  use  this  urine  for  the  tests. 

Trommers  test.  A  few  drops  (2-4)  of  a  5  per  cent,  solution  of 
cupric  sulphate  are  added  to  about  5  to  8  c.c.  of  urine  in  a  test-tube 
and  then  an  equal  volume  of  potassium  (or  sodium)  hydroxide  solu- 
tion is  added.  The  alkaline  hydroxide  precipitates  both  earthy  phos- 
phates and  cupric  hydroxide,  the  latter,  however,  dissolving  (espe- 
cially if  sugar  be  present)  in  the  excess  of  the  alkali,  producing  a 
beautiful  blue  transparent  liquid.  (If  no  sugar  is  present,  the  color 
is  less  blue,  but  more  of  a  greenish  hue.)  The  liquid  is  now  heated, 
when,  if  sugar  be  present,  a  yellow  precipitate  of  cuprous  hydroxide 
is  formed  which  subsequently  loses  its  water  and  becomes  the  red 
cuprous  oxide,  which  falls  to  the  bottom  or  adheres  to  the  sides  of 
the  test-tube.  (Plate  VIII.,  5.) 

As  various  organic  substances  (other  than  sugar)  have  a  tendency 
to  reduce  cuprous  oxide  at  a  temperature  of  100°  C.  (212°  F.),  it  is 
well  to  set  aside  a  test-tube  prepared  as  above  (without  heating  it) 
for  from  six  to  twenty-four  hours.  If  sugar  be  present,  the  forma- 
tion of  cuprous  hydroxide  will  gradually  take  place,  whilst  most 
other  orgonic  matters  do  not  act  upon  cupric  oxide  at  ordinary 
temperature. 

In  drawing  conclusions  from  the  above  test,  it  should  be  remem- 
bered that  a  change  of  color  does  not  indicate  sugar ;  that  a  precipi- 
tate of  earthy  phosphates  must  not  be  mistaken  for  cuprous  oxide  ; 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       471 

and  that  substances  other  than  sugar  may  deoxidize  cupric  oxide  at 
the  temperature  of  100°  C.  (212°  F.). 

Fehling's  test  differs  from  Trommer's  test  in  merely  using  a  pre- 
viously mixed  reagent  instead  of  producing  this  reagent,  as  it  were, 
in  the  urine  by  adding  to  it  cupric  sulphate  and  an  alkaline  hydroxide 
successively.  This  reagent,  known  as  Fehling's  solution,  or  as  alkaline 
cupric  tartrate  volumetric  solution,  is  made  by  mixing  exactly  equal 
volumes  of  the  below-mentioned  copper  solution  and  the  Kochelle 
salt  solution  at  the  time  required. 

Copper  solution : 

Crystallized  cupric  sulphate      ...'..       34.64  grammes. 
Water,  sufficient  quantity  to  make    ....     500  c.c. 

Rochelle  salt  solution : 

Potassium  sodium  tartrate 173  grammes. 

Potassium  hydroxide .125         " 

Water,  sufficient  quantity  to  make         ....     500  c.c. 

Both  solutions  are  preserved  in  small  well-stoppered  bottles,  and 
mixed  only  at  the  time  needed,  because  the  mixture  is  apt  to  decom- 
pose when  kept  some  time. 

The  addition  of  sodium-potassium  tartrate  in  Fehling's  solution  prevents  the 
precipitation  of  cupric  hydroxide  by  the  alkaline  hydroxide.  This  action  is 
analogous  to  the  formation  of  the  soluble  scale  compounds  of  iron,  where  the 
precipitation  of  ferric  hydroxide  is  also  prevented  by  tartaric  or  other  organic 
acids. 

While  Fehling's  solution  is  used  chiefly  for  quantitative  determina- 
tions, it  can  also  be  used  to  advantage  for  qualitative  tests.  This  is 
done  by  heating  about  10  c.c.  of  Fehling's  solution  in  a  test-tube, 
and  adding  drop  by  drop  the  suspected  urine ;  if  the  latter  contains 
larger  quantities  of  sugar  a  yellow  or  red  precipitate  of  cuprous  hy- 
droxide and  oxide  will  be  produced  very  readily ;  if  but  small  quan- 
tities are  present,  an  equal  volume  of  urine  may  be  added  to  the 
solution,  and  the  boiling  repeated  several  times  before  the  reaction 
takes  place. 

Bdtger's  bismuth  test  consists  in  adding  to  a  mixture  of  equal 
volumes  of  urine  and  potassium  (or  sodium)  hydroxide  solution  a 
few  grains  of  subnitrate  of  bismuth  and  boiling  for  half  a  minute. 
If  sugar  be  present,  a  gray  or  dark-brown,  finally  black,  precipitate 
of  bismuthous  oxide,  Bi2O2,  or  of  metallic  bismuth  is  formed.  If  but 
very  little  sugar  is  present,  the  undecomposed  excess  of  bismuthic 
nitrate  (or  bismnthic  hydroxide)  mixes  with  the  metallic  bismuth, 


472  PHYSIOLOGICAL  CHEMISTRY. 

imparting  to  it  a  gray  color  ;  the  test  should  then  be  repeated  with  a 
smaller  amount  of  the  bismuth  salt.     (Plate  VIII.,  6.) 

The  above  test  may  be  somewhat  modified  by  using  a  bismuth 
solution,  instead  of  the  powder.  The  solution  known  as  Nylander's 
reagent  is  made  by  dissolving  2  grammes  of  bismuth  subnitrate,  4 
grammes  of  Rochelle  salt,  and  10  grammes  of  sodium  hydroxide  in 
90  c.c.  of  water,  and  filtering.  One-half  c  c.  of  this  solution  is  heated 
with  about  5  c.c.  of  urine,  when,  in  the  presence  of  sugar,  a  brown  or 
black  precipitate  will  form  after  a  few  minutes. 

If  the  urine  contains  hydrogen  disulphide  (sometimes  produced  by  decom- 
position of  certain  urinary  constituents),  black  bismuth  sulphide  will  be 
formed,  which  may  be  mistaken  for  metallic  bismuth ;  albumin  itself  may  be 
the  cause  of  the  formation  of  alkaline  sulphides :  the  previous  complete  separa- 
tion of  albumin  is  therefore  indispensable. 

Moore's  or  Seller's  test  is  made  by  heating  urine  with  about  one- 
fourth  of  its  volume  of  solution  of  potassium  hydroxide.  In  the 
presence  of  sugar  the  color  of  the  mixture  will  deepen  to  a  dark 
yellow  or  brown,  and  the  depth  of  color  is  a  fair  indication  of  the 
quantity  of  sugar  present.  In  case  but  a  slight  change  takes  place 
in  color,  it  is  well  to  compare  it  with  that  of  an  unchanged  specimen 
of  the  urine. 

The  fermentation  test  is  based  upon  the  decomposition  of  sugar  by 
the  action  of  yeast  with  generation  of  carbon  dioxide.  The  test  is 
made  by  adding  to  about  50  or  100  c.c.  of  urine  (contained  in  a  large 
test-tube  or  small  flask)  a  few  grammes  of  common  yeast.  The  vessel 
containing  the  urine  is  provided  with  a  perforated  cork,  through 
which  is  passed  one  limb  of  a  bent  glass  tube,  long  enough  to  reach 
nearly  to  the  bottom  of  the  vessel,  which  should  be  completely  filled 
with  urine.  Under  the  second  limb  of  the  bent  glass  tube  is  placed 
a  beaker. 

The  apparatus  thus  prepared  is  placed  in  a  room  having  a  tem- 
perature of  about  22°-28°  C.  (72°-82°  F.).  If  sugar  be  present,  fer- 
mentation will  commence  within  twelve  hours,  and  will  manifest 
itself  by  the  formation  of  carbon  dioxide,  which  will  force  a  portion 
of  the  fluid  through  the  bent  tube  into  the  beaker  placed  there  for 
its  reception. 

The  disadvantages  of  this  process  are  the  length  of  time  required  for  its  per- 
formance, the  unreliability  of  the  ferment,  and  the  fact  that  small  quantities  of 
sugar  (less  than  0.5  per  cent.)  evolve  so  little  carbon  dioxide  that  a  doubt  may 
be  felt  as  to  the  presence  of  sugar  at  all. 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE       473 

Picric  acid  test  for  sugar.  It  has  been  mentioned  above  that  picric 
acid  serves  as  an  excellent  reagent  for  albumin  ;  in  the  presence  of 
alkalies  it  may  also  be  used  to  advantage  as  a  reagent  for  sugar. 
Urine  is  mixed  with  a  few  drops  of  a  saturated  aqueous  solution  of 
picric  acid,  a  little  caustic  potash  is  added  and  gently  heated;  a 
marked  reddish  or  reddish-brown  coloration,  due  to  the  formation  of 
picramic  acid,  H.C6H2.NH2.(NO2)2O,  indicates  sugar.  A  reddish 
color  which  appears  without  heating  the  mixture  and  which  disap- 
pears completely  within  twenty  minutes  indicates  the  presence  of 
kreatinin.  A  portion  of  the  reddish  liquid  heated  will  turn  more 
intensely  red  if  sugar  is  also  present. 

Molisctis  test.  This  is  made  by  adding  to  urine  a  few  drops  of  a 
10  per  cent,  alcoholic  solution  of  either  thymol,  menthol,  or  alpha- 
naphthol.  Into  the  inclined  test-tube  about  2  c.c.  of  concentrated 
sulphuric  acid  are  then  poured  so  as  to  form  a  layer  below  the  urine. 
At  the  zone  of  contact  a  color  is  produced  which  is  red  with  thymol 
and  menthol,  violet  with  greenish  borders  with  alpha-naphthol. 
Traces  of  glucose  are  shown  by  these  tests. 

Phenyt-hydrazine  test  is  made  by  heating  to  boiling  a  mixture  of 
equal  volumes  of  urine  and  potassium  hydroxide  solution,  to  which  a 
few  drops  of  phenyl-hydrazine  have  been  added.  In  the  presence  of 
sugar  the  mixture  assumes  an  intense  yellow  or  orange  color.  Upon 
supersaturating  the  cooled  mixture  with  acetic  acid  a  precipitate 
of  golden  yellow,  r  needle-shaped  crystals  of  phenyl-dextros-azon  is 
formed.  The  test  has  the  advantage  that  glucose  is  the  only  sub- 
stance likely  to  occur  in  urine,  which  forms  these  crystals. 

Quantitative  estimation  of  sugar.  By  far  the  best  method  is 
the  decomposition  of  a  copper  solution  of  a  known  strength,  and 
Fehling's  solution  prepared  as  stated  above,  answers  this  purpose 
well. 

1000  c.c.  of  Fehling's  solution,  containing  34.64  grammes  of  crys- 
tallized cupric  sulphate,  CuSO4.5H2O,  are  decomposed  by  5  grammes 
of  grape-sugar,  or  1  c.c.  of  solution  by  0.005  of  grape-sugar. 

To  make  the  quantitative  determination,  operate  as  follows  :  10  c.c. 
of  Fehling's  solution  are  poured  into  a  porcelain  dish  of  about  200  c.c. 
capacity,  placed  over  a  flame.  The  copper  solution  is  diluted  with 
about  40  c.c.  of  water,  and  heated  to  boiling  ;  to  the  boiling  liquid, 
urine  (which  has  been  previously  diluted  with  9  parts  of  water)  is 
added  from  a  burette  very  gradually,  until  the  blue  color  of  the  solu- 
tion has  disappeared,  and  there  remains,  upon  subsidence  of  the 


474  PHYSIOLOGICAL  CHEMISTRY. 

cuprous  oxide,  an  almost  colorless,  clear  liquid.  A  filtered  portion 
of  this  liquid,  acidified  with  hydrochloric  acid,  should  not  give  a 
reddish-brown  precipitate  with  potassium  ferrocyanide  (a  precipitate 
would  show  that  all  copper  had  not  been  precipitated,  and  that  more 
urine  was  needed),  whilst  a  second  portion  of  the  filtered  fluid  should 
not  produce  a  red  precipitate  on  boiling  with  a  few  drops  of  Fehling's 
solution  (a  precipitate  would  indicate  that  too  much  urine  had  been 
added,  in  which  case  the  operation  has  to  be  repeated). 

The  calculation  of  the  amount  of  sugar  present  is  easily  made. 
10  c.c.  of  Fehling's  solution  are  decomposed  by  0.05  gramme  of 
sugar ;  this  quantity  must,  therefore,  be  contained  in  the  number  of 
c.c.  of  urine  used.  Suppose  30  c.c.  of  urine,  diluted  with  9  parts  of 
water,  or  3  c.c.  of  pure  urine,  have  been  required  to  decompose  the  10 
c.c.  of  Fehling's  solution,  then  3  c  c.  of  urine  contain  of  grape-sugar 
0.05  gramme,  or  100  c.c.  of  urine  1.666  grammes,  according  to  the 
proportion  : 

3     :     0.05     :  :     100    :     x 

3  =  1.688. 

If  the  urine  contains  but  very  little  sugar,  it  may  be  used  directly 
without  diluting  it,  or  instead  of  diluting  it  with  9  parts  of  water,  it 
may  be  diluted  with  4  volumes  or  with  an  equal  volume  of  water. 

Determination  by  fermentation.  The  fermentation  test  above  described  can  be 
used  for  quantitative  determination  of  sugar,  provided  the  quantity  present  is 
not  less  than  0.5  per  cent.,  when  the  results  are  fairly  accurate.  The  determi- 
nation is  made  by  observing  carefully  the  specific  gravity  of  the  urine  at  the 
same  temperature  before  and  after  fermentation.  The  decomposition  of  the 
sugar  causes  the  specific  gravity  to  become  less,  and  every  degree  of  the  urin- 
ometer  indicates  0.219  per  cent,  of  sugar.  If,  for  instance,  urine  showed  a  spe- 
cific gravity  of  1032  before,  and  1022  after  fermentation,  the  quantity  of  sugar 
present  is  10  times  0.219,  or  2.19  per  cent.  The  yeast  to  be  used  for  the  experi- 
ment should  be  well  washed  upon  a  filter  with  pure  water,  and  the  urine 
quickly  filtered  before  taking  its  specific  gravity  after  fermentation  has  taken 
place. 

Experiment  77.  Determine  the  amount  of  sugar  in  urine  by  the  methods 
described  above.  If  no  suitable  urine  is  to  be  had,  add  some  glucose  to  urine 
and  use  this  solution. 

Detection  of  bile.  The  presence  of  bile  in  urine  is  generally 
indicated  by  a  decided  color,  which  varies  from  a  deep  brownish-red 
to  a  dark  brown ;  the  foam  of  such  urine  (produced  by  shaking)  has 
a  distinct  yellow  color,  and  a  piece  of  filtering-paper  or  a  piece  of 
linen  dipped  into  the  urine  assumes  a  yellow  color,  which  does  not 
disappear  on  drying. 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       475 

The  further  detection  of  bile  depends  upon  the  reactions  of  the 
biliary  coloring  matters  or  biliary  acids;  it  frequently  happens, 
however,  that  the  pigments  are  present,  whilst  the  acids  are  not. 

Gmelin's  test  for  biliary  coloring  matters  has  been  considered  al- 
ready, and  may  be  applied  to  urine  either  by  allowing  a  small  quan- 
tity of  nitric  acid,  containing  some  nitrous  acid,  to  flow  down  the  sides 
of  a  test-tube  (containing  the  urine)  in  such  a  manner  that  the  two 
fluids  do  not  mix,  or  by  placing  upon  a  porcelain  plate  a  few  drops 
of  the  urine,  near  it  a  few  drops  of  nitric  acid,  to  which  one  drop  of 
sulphuric  acid  has  been  added,  and  allowing  the  two  liquids  to  ap- 
proach gradually.  In  both  cases  (if  bile  pigment  is  present)  a  play  of 
color  is  seen  at  the  point  of  union  between  the  two  fluids,  the  colors 
changing  from  green  to  blue,  violet-red,  and  yellow  or  yellowish- 
green.  While  the  appearance  of  the  green  at  the  beginning  is  indis- 
pensable to  prove  the  presence  of  bile,  the  presence  of  all  the  other 
colors  is  not  essential.  (Plate  VIII.,  7.) 

The  above  test  may  be  made  in  a  somewhat  modified  form  by  mix- 
ing the  urine  with  a  concentrated  solution  of  sodium  nitrate,  and 
pouring  down  the  sides  of  the  test-tube  concentrated  sulphuric  acid  in 
such  a  manner  as  to  form  two  distinct  layers  ;  the  colors  are  seen  at 
the  point  of  contact  as  above. 

If  the  urine  be  very  dark  in  color,  it  should  be  diluted  with  water 
before  applying  the  above  tests. 

Ultzmann's  test  for  bile  pigment  is  made  by  mixing  10  c.c.  of  urine 
with  3  or  4  c.c.  of  potassium  hydroxide  solution  (1  in  3  of  water), 
and  supersaturating  with  hydrochloric  acid ;  the  mixture  assumes  a 
beautiful  emerald-green  color  after  some  time. 

Pettenkofer' 's  test  for  biliary  acids  is  made  by  dissolving  a  few  grains 
of  cane-sugar  in  urine  contained  in  a  test-tube,  and  allowing  some 
concentrated  sulphuric  acid  to  trickle  down  the  side  of  the  inclined 
test-tube  ;  a  purple  band  is  seen  at  the  upper  margin  of  the  acid,  and 
on  slightly  shaking  the  liquid  becomes  at  first  turbid,  then  clear,  and 
almost  simultaneously  it  turns  yellow,  then  pale  cherry-red,  dark  car- 
mine-red, and  finally  a  beautiful  purple  violet.  The  temperature 
must  not  be  allowed  to  rise  much  above  38°  C.  (100°  F.)  (Plate 
VIII.,  8.) 

As  many  substances  (other  than  biliary  acids)  show  a  similar 
reaction,  it  is  often  necessary  to  separate  the  bile  acids  by  the  process 
described  in  connection  with  the  consideration  of  bile  itself. 

In  case  the  quantity  of  biliary  constituents  is  so  small  that  they 
cannot  be  noticed  by  the  tests  mentioned,  the  urine  should  be  shaken 


476  PHYSIOLOGICAL  CHEMISTRY. 

with  about  one-fourth  of  its  volume  of  chloroform,  which  dissolves 
the  biliary  matters.  Some  of  this  solution  is  dropped  upon  blotting 
paper,  and  after  evaporation  a  drop  of  red  fuming  nitric  acid  is 
placed  in  the  centre  of  the  remaining  stain,  when  concentric  color  rings 
appear.  The  second  portion  of  chloroform  solution  is  evaporated 
and  the  residue  used  for  making  the  reactions  as  described  above. 

Diazo-reaction.  Some  abnormal  constituent  (which  has  not  yet 
been  isolated)  is  found  in  the  urine  of  persons  suffering  from  typhoid 
fever.  The  presence  of  this  unknown  substance  is  indicated  by  a 
very  characteristic  reaction  with  diazo-benzol-sulphonic  acid,  which 
compound  is  produced  by  the  action  of  nitrous  acid  on  sulphanilic 
acid.  Two  solutions  are  required  :  a.  2  grammes  of  sulphanilic  acid 
dissolved  in  a  mixture  of  50  c.c.  of  hydrochloric  acid  and  1000  c.c. 
of  water ;  b.  A  0.5  per  cent,  solution  of  sodium  nitrite.  To  perform 
the  reaction  50  parts  of  a  and  1  part  of  6  are  mixed,  and  equal 
volumes  of  the  reagent  and  of  urine  are  mixed  in  a  test-tube  and 
saturated  with  ammonia.  In  those  cases  in  which  the  reaction  is 
positive  the  solution  assumes  a  carmine-red  color,  which,  on  shaking, 
must  also  be  visible  in  the  foam.  If  the  test-tube  is  allowed  to  stand 
twenty-four  hours,  a  greenish  precipitate  is  formed.  Normal  urine, 
thus  treated,  shows  a  deep  yellow  or  orange  color ;  the  precipitated 
phosphates  as  well  as  the  foam  are  colorless. 

While  the  reaction  is  also  found  in  some  cases  of  measles,  sepsis,  scarlet 
fever,  etc.,  yet  its  constant  and  early  presence  in  typhoid  fever  and  its  presence 
in  severe  cases  of  pulmonary  tuberculosis  make  the  reaction  of  considerable 
diagnostic  and  prognostic  importance  in  these  diseases. 

Acetone  and  diacetic  acid.  Both  of  these  substances  appear  in 
considerable  quantities  in  the  urine  when  there  is  marked  destruction 
of  the  protoplasm  of  the  body ;  they  are  more  especially  found  in 
cases  of  high  fever,  in  some  cases  of  cancer,  and  in  severe  forms  of 
diabetes.  Large  quantities  of  acetone  appear  in  the  urine  during 
disturbances  of  digestion  and  in  intestinal  diseases. 

Diacetic  acid,  CH3.COCH2.CO2H,  is  recognized  by  means  of 
Gerhard's  ferric  chloride  reaction.  A  solution  of  ferric  chloride 
added  to  the  urine  produces  a  gray  precipitate  of  ferric  phosphate ; 
upon  the  further  addition  of  the  iron  solution  a  deep  bordeaux  color 
appears.  The  foam  produced  on  shaking  the  test-tube  is  reddish- 
violet.  On  the  addition  of  sulphuric  acid  the  red  color  disappears. 
Diacetic  acid  readily  decomposes  with  the  formation  of  acetone. 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.      477 

Acetone  is  recognized  in  the  following  manner  :  500  c.c.  of  urine 
are  acidified  with  a  few  drops  of  hydrochloric  acid  and  distilled.  To 
the  distillate  a  few  drops  of  iodine  solution  (1  iodine,  2  potassium 
iodide,  100  water),  and  of  potassium  hydroxide  are  added.  If  acetone 
is  present  a  characteristic  yellowish-white  precipitate  of  iodoform  is 
formed. 

Urinary  deposits  (sediments).  Normal  urine  is  always  clear,  but 
occasionally,  and  particularly  in  abnormal  conditions,  it  is  turbid. 

Urine  may  be  turbid  when  passed,  and  this  indicates  an  excess 
of  mucus,  or  the  presence  of  renal  epithelium,  pus,  blood,  chyle, 
semen,  bile,  or  phosphate  or  urate  of  sodium  in  excess,  etc.  A 
turbidity  subsequent  to  the  passage  of  the  urine  is  generally  due 
to  the  precipitation  of  phosphates  or  tirates,  or  it  may  result  from 
fermentation  or  decomposition.  Either  of  the  substances  named  will 
form  a  deposit  on  standing. 

When  such  a  deposit  is  to  be  examined,  a  few  ounces  of  the  urine 
should  be  set  aside  for  several  hours  in  a  tall,  narrow,  cylindrical 
glass ;  when  the  sediment  has  collected  at  the  bottom,  the  supernatant 
urine  may  be  decanted,  or  the  sediment  may  be  taken  out  by  means 
of  a  pipette  for  examination. 

Sediments  are  either  organized  or  unorganized.  To  the  first 
belong  :  mucus,  blood,  pus,  urinary  casts,  epithelium,  spermatozoids, 
fungi,  infusoria,  etc. ;  to  the  second  belong:  uric  acids,  u rates,  cal- 
cium oxalate,  phosphate,  or  carbonate,  magnesium-ammonium  phos- 
phate, cystin,  hippuric  acid,  etc. 

The  chemical  examination  of  any  urinary  sediment  should  always 
be  preceded  by  a  microscopical  examination,  which  latter  is  in  many 
cases  the  only  way  of  determining  the  nature  of  the  sediment,  espe- 
cially of  the  organized  substances.  Most  of  the  unorganized  and 
either  crystalline  or  amorphous  sediments  may  be  easily  recognized 
by  chemical  means. 

Urates  of  ammonium,  calcium,  and  sodium  dissolve  on  heating  the 
urine,  and  are  reprecipitated  on  cooling.  The  murexid  test  is  used 
in  addition. 

Phosphates  of  calcium  or  ammonium-magnesium  dissolve  in  acetic 
acid,  and  ammonium  molybdate  dissolved  in  nitric  acid  produces  a 
yellow  precipitate  on  heating. 

Calcium  oxalate  is  insoluble  in  acetic,  but  soluble  in  hydrochloric 
acid,  from  which  solution  it  is  reprecipitated  on  neutralizing  with 
ammonia. 


478  PHYSIOLOGICAL  CHEMISTRY. 

Uric  acid  is  not  dissolved  by  heat,  nor  by  acetic  or  hydrochloric 
acid,  but  dissolves  on  the  addition  of  caustic  potash  and  burns  on 
platinum  foil  without  leaving  a  residue  ;  it  is  recognized  by  the 
murexid  test. 

Oystin  is  insoluble  in  water  and  alcohol,  but  soluble  in  mineral 
acids  and  in  caustic  alkalies;  from  either  solution  it  is  reprecipitated 
by  neutralizing.  Cystin  contains  26  per  cent,  of  sulphur,  which 
causes  the  formation  of  black  sulphide  of  lead  when  cystin  is  boiled 
with  caustic  potash  to  which  a  few  drops  of  solution  of  lead  acetate 
have  been  added. 

Urinary  calculi  are  solid  deposits  of  larger  or  smaller  size  formed 
from  the  urine  within  the  tracts  (kidneys,  ureter,  bladder,  and  urethra). 

The  chemical  composition  of  the  calculi  is  generally  that  of  either 
of  the  above-named  unorganized  sediments,  and  their  nature  can 
easily  be  determined  by  using  the  following  method  : 

Make  a  section  through  the  centre  of  the  calculus,  scrape  some  of 
the  substance  off,  powder  it  finely,  and  heat  some  of  it  on  platinum 
foil.  It  may  either  burn  away  completely  (uric  acid,  urate  of  ammo- 
nium, cystin,  xanthin)  or  may  be  partially  combustible  (urates  or 
oxalates),  or  may  be  incombustible  (chiefly  phosphates).  A  slight 
blackening  occurs  generally,  even  in  heating  a  calculus  consisting  of 
incombustible  matter,  and  is  due  to  the  presence  of  traces  of  organic 
urinary  constituents. 

If  completely  combustible,  digest  a  little  of  the  powder  with  dilute 
hydrochloric  acid ;  cystin  and  xanthin  are  dissolved,  uric  acid  remains 
undissolved.  Apply  murexid  test  for  uric  acid,  the  above-mentioned 
lead  test  for  cystin,  and  for  xanthin  test  by  dissolving  a  little  of  the 
calculus  in  nitric  acid  and  evaporating  to  dryness,  when  in  the 
presence  of  xanthin  a  bright-yellow  residue  will  be  left,  which  becomes 
violet-red  when  treated  with  caustic  potash.  In  case  uric  acid  has 
been  found,  it  may  be  in  combination  with  ammonia,  which  may  be 
verified  by  heating  the  powder  with  a  little  caustic  potash,  when 
ammonia  gas  is  liberated,  which  may  be  recognized  by  its  action  on 
red  litmus-paper,  odor,  etc. 

If  partially  combustible  or  incombustible,  digest  some  of  the  powder 
with  dilute  hydrochloric  acid.  If  it  dissolves  completely,  uric  acid  is 
not  present.  If  a  residue  be  left,  apply  the  murexid  test.  To  a 
portion  of  the  solution  add  ammonium  molybdate  and  heat;  a  yellow 
precipitate  indicates  phosphoric  acid.  To  another  portion  add  am- 
monia water  and  then  excess  of  acetic  acid ;  a  white  pulverulent 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE,       479 

residue  indicates  calcium  oxalate,  which  can  be  verified  by  igniting 
some  of  the  calculus  and  adding  a  drop  of  acid,  when  effervescence 
will  be  noticed,  the  oxalate  having  been  converted  into  a  carbonate 
by  the  ignition  ;  the  solution  thus  obtained  can  be  tested  for  calcium 
by  the  addition  of  water  of  ammonia  and  ammonium  oxalate.  In 
case  phosphoric  acid  has  been  found,  this  is  present  either  as  a  cal- 
cium or  magnesium-ammonium  salt.  To  distinguish  between  them, 
neutralize  the  solution  of  the  powder  in  hydrochloric  acid  with 
ammonia,  add  acetic  acid  and  ammonium  oxalate ;  a  white  precipi- 
tate indicates  calcium ;  if  no  precipitate  is  produced,  supersaturate 
with  ammonia,  when  the  crystalline  magnesium-ammonium  phos- 
phate will  gradually  form. 

Most  common  are  calculi  of  uric  acid  ;  often  met  with  are  those  of 
urates,  phosphates,  and  oxalates ;  rarely,  however,  those  of  xanthin 
and  cyst  in. 

Microscopical  examination  of  urinary  sediments.  The  chemi- 
cal examination  of  any  urinary  sediment  should  always  be  preceded 
by  a  microscopical  examination,  which  latter  is  in  many  cases  the 
only  way  of  determining  the  nature  of  the  sediment,  especially  of  the 
organized  substances. 

Fig.  44,  A-O,  shows  the  principal  sediments  found  in,  or  produced 
from,  urine,  as  seen  with  a  magnifying  power  of  200  diameters. 

A.  Uric  add  occurs  in  many  different  forms,  mostly  in  rhombic 
plates,  with  rounded  obtuse  angles,  often  joined  into  rosettes.     Uric 
acid  is  found  almost  invariably  colored  red  or  reddish-brown,  which 
generally  distinguishes  it  from  other  sediments.      The  crystals  or 
clusters  of  crystals  are  often  large  enough  to  be  seen  by  the  naked 
eye,  and  are  then  known  by  the  terms  "sand,"  "gravel,"  or  "red- 
pepper  grains." 

B.  Ammonium  add  urate  is  found,  generally  associated  with  amor- 
phous or  crystalline  phosphates,  in  urine  which  has  become  alkaline. 
The  crystalline  globules  are  generally  covered  with  spinous  excres- 
cences, which  give  them  the  characteristic  "thorn-apple"  appearance. 

C.  Sodium  urate  forms  generally  a  part  in  the  pulverulent,  heavy, 
variously  tinted  deposit  of  the  mixed  urates  known  as  "brickdust"or 
"  lateritious  "  sediment.     It  occurs  either  in  fine  amorphous  granules 
which  cannot  be  distinguished  microscopically  from  other  amorphous 
sediments  or  in  a  crystalline  form  as  shown  in  the  figure. 

D.  Urea  nitrate  crystallizes  readily  in  large  six-sided  plates  on  the 
addition  of  nitric  acid  to  urine. 


480  PHYSIOLOGICAL  CHEMISTRY. 

E.  1,  Leucin,  or  amido-caproic  acid,  C6Hn(NH2)O2 ;  and  2,  Tyrosin, 
C9HUNO3,  are  but  rarely  met  with  in  urinary  deposits.     Leucin  is 
found  either  as  rounded  lumps,  showing  but  little  crystalline  struc- 
ture, or  as  spherical  masses,  exhibiting  fine  radial  striation.    Tyrosin 
appears  generally  in  fine,  long,  silky  needles,  forming  bundles  or 
rosettes. 

F.  Oystin  occurs  occasionally  as  a   grayish,  crystalline   deposit, 
forming  transparent  six-sided  plates ;  it  also  occurs  in  calculi.     The 
latter  may  be  recognized  by  the  above-mentioned  chemical  properties 
or  by  dissolving  a  little  in  hydrochloric  acid  and  neutralizing  with 
ammonia,  when  cystin  is  reprecipitated  and  shows  the  characteristic 
six-sided  plates  under  the  microscope. 

G.  Magnesium-ammonium  phosphate,  or  triple  phosphate,  MgNH4- 
PO4.6H2O,  is  found  generally  in  triangular  prisms  with  bevelled 
ends,  as  shown  in  1,  but  sometimes  also  in  star-shaped,   feathery 
crystals,  represented  in  2. 

H.  Calcium  phosphate,  Ca3(PO4)2,  is  most  frequently  found  in 
amorphous  globules,  but  also  crystallized  either  in  prisms,  1,  or  in 
'*  wedge-shaped  "  crystals,  2. 

I.  Calcium  oxalate,  CaC2O4,  occurs  either  in  quadratic  octohedra 
with  brilliant  refraction,  1,  or  sometimes  in  the  shape  of  "dumb- 
bells," 2. 

J.  Blood  corpuscles  appear  under  the  microscope  as  reddish,  circular 
disks,  sometimes  laid  together  in  strings.  If  seen  in  profile,  they 
appear  biconcave.  1,  shows  the  corpuscles  in  a  fresh  condition;  2, 
as  generally  seen  in  urine. 

K.  Mucus  and  pus  are  often  difficult  to  distinguish  from  each 
other  under  the  microscope,  as  they  both  appear  as  little  granular 
globules,  varying  somewhat  in  appearance  with  the  reaction  of  the 
urine.  Pus  is  rendered  slimy,  ropy,  viscid,  and  tenacious  by  the 
addition  of  caustic  potash.  1,  shows  globules  of  mucus  ;  2,  of  pus; 
and  3,  of  pus  treated  with  acetic  acid,  which  clears  up  the  granular 
globules  with  the  appearance  of  a  nucleus. 

L.  Hcemin  crystals.  The  formation  of  these  crystals  often  serves 
to  recognize  blood,  and  is  accomplished  by  mixing  the  latter  on  a 
glass  slide  with  a  trace  of  sodium  chloride  and  a  drop  of  glacial 
acetic  acid  and  warming  gently,  when  the  characteristic  crystals  will 
appear.  By  repeating  the  process  several  times,  larger  and  better- 
developed  crystals  are  obtained. 

M.  1,  Hyaline  casts;  2,  Granular  casts.  Urinary  casts  are  tube- 
like  cylinders,  often  found  together  with  blood  and  pus  corpuscles,  or 


EXAMINATION  OF  NORMAL  AND  ABNORMAL  URINE.       481 

FIG.  44. 
A  B 


2>&\V 


Pd 

?i 

-6° 


I  2 

L 

rt     K  V        ^ 


'€^V 


0 


Urinary  sediments. 
31 


482  PHYSIOLOGICAL  CHEMISTRY. 

holding  in  their  substance  or  walls  epithelial  cells,  raucous  corpuscles, 
and  fat  globules.  Hyaline  casts  are  distinguished  by  their  trans- 
parent appearance,  while  granular  casts  show  a  more  or  less  granular 
surface. 

N.  Epithelial  casts  and  cells.  According  to  the  origin  (vagina, 
urethra,  bladder,  etc.)  of  these  bodies,  they  differ  somewhat,  and  it 
is  difficult  to  recognize  with  certainty  the  source  whence  they  are 
derived. 

O.  1,  Waxy  casts;  2,  Casts  with  blood  corpuscles ;  3,  Casts  with  fat 
globules.  Waxy  casts  resemble  hyaline  casts,  but  are  less  transparent. 
Casts  containing  blood  corpuscles  or  fat  globules  are  generally  easily 
recognized. 

In  addition  to  the  above-mentioned  urinary  deposits  there  may 
also  be  found  various  kinds  of  fungi,  vibriones,  spermatozoids,  hair, 
or  even  such  foreign  matters  as  fibres  of  cotton,  wool,  or  silk,  with 
the  characteristic  appearance  of  which  the  student  should  familiarize 
himself  thoroughly. 

QUESTIONS. — 551.  What  points  are  to  be  considered,  and  what  substances 
determined,  in  the  analysis  of  normal  and  abnormal  urine?  552.  What  is  the 
color  of  urine,  and  what  are  the  chief  causes  influencing  the  color  ?  553.  What 
is  the  specific  gravity  of  healthy  urine,  how  is  it  determined,  and  how  is  the 
total  amount  of  solids  approximately  calculated  from  the  specific  gravity? 
554.  Describe  the  different  tests  by  which  albumin  may  be  recognized,  and 
state  the  precautions  necessary  in  making  these  tests.  555  How  may  the  quan- 
tity of  albumin  in  urine  approximately  and  how  accurately  be  determined? 

556.  Describe  the  various  tests  for  sugar.     On  what  principles  are  they  based? 

557.  How  is  sugar  determined  quantitatively?    558.  By  what  tests  are  biliary 
pigments  and  acids  recognized  in  urine  ?    559.  What  is  the  nature  of  urinary 
sediments,  and  by  what  means  are  they  recognized?     560.  What  are  urinary 
calculi  generally  composed  of,  and  by  what  simple  tests  can  their  nature  be 
determined  ? 


APPENDIX. 


TABLE  OF  WEIGHTS  AND  MEASURES. 


length. 


1  millimeter    =        0.001  meter    = 

0.0394  inch. 

1  centimeter    =        0.01    meter    = 

0.3937  inch. 

1  decimeter     =        0.1      meter    = 

3.9371  inches. 

1  meter 

39.3708  inches. 

1  decameter     =       10         meters  = 

32.8089  feet. 

1  hectometer   =    100        meters  = 

328.089    feet. 

1  kilometer      =  1000         meters  = 

0.6214  mile. 

1  yard  or  36  inches 

0.9144  meter. 

1  inch 

25.4        millimeters. 

1  milliliter 
1  centiliter 
1  deciliter 
1  liter 
1  decaliter 
1  hectoliter 
1  kiloliter 
1  U.  S.  gallon 
1  imperial  gallon 
1  minim 
1  fluidrachm 
1  fluidounce 
1  liter 


Measures  of  capacity. 

=        1  c.c.  =        0.001  liter    : 

=      10  c.c.  =r        0.01  liter    = 

=    100  c.c.  =        0.1  liter    = 
=  1000  c.c. 

=      10  liters  = 

=    100  liters  = 

=  1000  liters  = 


0.0021 
0.0211 
0.2113 
1.0567 
2.6418 
26.418 
264.18 
3785.3 
45435 
0.06 
3.70 
29.57 
33.81 


U.  S.  pint. 

U.  S.  pint. 

U.  S  pint. 

U.  S.  quart. 

U.  S.  gallons. 

U.  S.  gallons. 

U.  S.  gallons. 

c.c. 

c.c. 

c.c. 

c.c. 

c.c. 

fluidounces. 


0.01 
0.1 


1  milligram  = 

1  centigram  = 

1  decigram  = 

1  gramme 

1  decagram  =       10 

1  hectogram  =     100 

1  kilogram  =  1000 

1  grain  Troy 

1  drachm  Troy 

1  ounce  Troy 

1  ounce  avoirdupois 

1  pound  avoirdupois 


Weights. 

0.001  gramme 
gramme 
gramme 


grammes 
grammes 
grammes 


0.015  grain     Troy. 
0.154  grain     Troy. 
1.543  grain     Troy. 
15.432  grains    Troy. 
154.324  grains    Troy. 
0.268  pound   Troy. 
2.679  pounds  Troy. 
0.0648  gramme. 
3.888    grammes. 
31.103    grammes. 
28.350    grammes. 
453.592    grammes. 

(483) 


484  APPENDIX. 

Commercial  weights  and  measures  of  the  U.  S.  A.  • 

1  pound  avoirdupois  =      16     ounces. 

1  ounce  =  437.5  grains. 

1  gallon  =  231     cubic  inches. 

1  gallon  =      4     quarts  =  8  pints. 

1  pint  of  water  weighs  7291.2  grains  at  a  temperature  of  15.6°. 

Troy  weight. 
1  drachm  =  60  grains. 
1  ounce     =    8  drachms  =  480  grains. 


TABLE  OF  ELEMENTS. 


Atomic 

Atomic 

Symbol. 

weight. 

Symbol. 

weight. 

Aluminum 

.     Al 

27.04 

Molybdenum 

.     Mo 

95.9 

Antimony  . 

.    Sb 

119.6 

Nickel 

.    Ni 

58.6 

Arsenic 

.    As 

74.9 

Nitrogen     . 

.    N 

14.01 

Barium 

.     Ba 

136.9 

Osmium 

.    Os 

190.3 

Beryllium1 

.    Be 

9.03 

Oxygen 

.    0 

15.96 

Bismuth     . 

.     Bi 

208.9 

Palladium  . 

.    Pd 

106.35 

Boron 

.     B 

10.9 

Phosphorus 

.    P 

30.96 

Bromine     . 

.     Br 

79.76 

Platinum    . 

.    Pt 

194.3 

Cadmium  . 

.     Cd 

111.5 

Potassium 

.     K 

39.03 

Caesium 

.     Cs 

132.7 

Rhodium 

.     Rh 

102.9 

Calcium 

.     Ca 

39.91 

Rubidium  . 

.    Rb 

85.2 

Carbon 

.    C 

11.97 

Ruthenium. 

.    Ru 

101.4 

Cerium 

.     Ce 

139.9 

Samarium  . 

.    Sm 

149.62 

Chlorine     . 

.     Cl 

35.37 

Scandium  . 

.    Sc 

43.97 

Chromium 

.     Cr 

52.0 

Selenium    . 

.    Se 

78.87 

Cobalt 

.     Co 

58.6 

Silicon 

.    Si 

28.3 

Columbium2 

.    Cb 

93.7 

Silver 

.    Ag 

107.66 

Copper 

.    Cu 

63.18 

Sodium 

.    Na 

23.0 

Didymium8 

.    Di 

142.0 

Strontium  . 

.    Sr 

87.3 

Erbium 

.     Er 

166.0 

Sulphur 

.     S 

31.98 

Fluorine     . 

.     F 

19.0 

Tantalum   . 

.    Ta 

182.0 

Gallium 

.    Ga 

69.9 

Tellurium  . 

.     Te 

125.0 

Germanium 

.    Ge 

72.3 

Terbium     . 

.    Tb 

159.1 

Gold  . 

.    Au 

196.7 

Thallium    . 

.    Tl 

203.7 

Hydrogen  . 

.    H 

1.0 

Thorium    . 

.    Th 

231.9 

Indium 

.     In 

113.6 

Tin     . 

.    Sn 

118.8 

Iodine 

.     I 

126.53 

Titanium    . 

.     Ti 

48.0 

Iridium 

.     Ir 

192.5 

Tungsten    . 

.     W 

183.6 

Iron    . 

.    Fe 

55.88 

Uranium    . 

.     U 

238.8 

Lanthanum 

.    La 

138.2 

Vanadium  . 

.    V 

51.1 

Lead  . 

.    Pb 

206.4 

Ytterbium  . 

.    Yb 

172.6 

Lithium 

.    Li 

7.01 

Yttrium 

.    Yt 

88.9 

Magnesium 

.    Mg 

24.3 

Zinc   . 

.     Zn 

65.1 

Manganese 

.    Mn 

54.8 

Zirconium  . 

.    Zr 

90.4 

Mercury     . 

.    Hg 

199.8 

1  Also  called  glucinum. 

2  Also  called  niobium. 

*  Composed  of  neo-  and  praseo-didymium. 


(485) 


INDEX. 


A  BSOKPTION,  34 
A     Acetanilid.  383 
Acetate  of  ammonium,  328 
Acetic  acid,  326 

analytical  reactions  of,  327 

aldehyde,  315 

ether*  343 
Acetone,  329,  476 
Acetylene,  305 
Acid,  abietic,  373 

acetic,  326 

adipic,  331 

aniline-para-sulphonic,  383 

arabic,  352 

arachidic,  325 

arsenic,  205 

arsenous,  208 

behenic,  325 

benzoic,  375 

boric,  98 

bromic,  123 

butyric,  329 

camphoric,  372 

capric,  324 

caproic,  324 

caprylic,  324 

carbamic,  357 

carbazotic,  371 

carbolic,  369 

carbonic,  95 

carminic,  354 

cathartic,  354 

cerotic,  325 

chloric,  121 

cholic,  441 

chromic,  177 

citric,  336 

copaivic,  374 

cyanic,  362 

diacetic,  476 

diazo-benzol  sulphonic,  383 

dithionic,  106 

fluoric,  127 

formic.  325 

fulminic,  364 

gallic,  379 

glacial  acetic,  327 
phosphoric,  113 

glycocholic,  441 

glycolic,  338 

hippuric,  458 

hyaenic,  325 


Acid,  hydriodic,  125 
hydrobromic,  123 
hydrochloric,  120 
hydrocyanic,  358 
hydroferricyanic,  362 
hydroferrocyanic,  362 
hydrofluoric,  127 
hydrosulphuric,  106,  235 
hypobromic,  123 
hypochlorous,  122 
hyponitrous,  89 
hypophosphorous,  115 
hyposulphurous,  106 
kinic,  395 
lactic,  338 
lauric,  324 
malic,  333 
malonic,  331 
manganic,  174 
margaric,  325 
meconic,  395 
melissic,  325 
metaphosphoric,  113 
muriatic,  120 
myristic,  324 
myronic,  354 
nicotinic,  386 
nitric,  89 

nitro-hydrochloric,  121 
nitro-muriatic,  121 
nitrous,  89 
renanthylic,  324 
oleic,  330 

orthophosphoric,  113 
oxalic,  331 
palmitic,  325 
pelargonic,  324 
pentath  ionic,  106 
perchloric,  121 
permanganic,  175 
phenol-sulphonic,  371 
phospho-molybdic,  389 
phosphoric,  113 
phosphorous,  113 
phthalic,  378 
picric,  371 
propionic,  324 
prussic,  358 
pyrogallic,  379 
pyrophosphoric,  113 
pyrosulphuric,  106 
pyrotartaric,  331 


(487) 


488 


INDEX. 


Acid,  rosolic,  256 

salicylic,  377 

sarco-lactic,  337 

silicic,  98 

stannic,  218 

stearic,  325 

succinic,  331 

sulphanilic,  383 

sulphocarbolic,  371 

sulphocyanic,  362 

sulphonic,  321 

sulphuric,  103 

sulphurous,  102 

tannic,  379 

tartaric,  333 

taurocholic,  441 

tetrathionic,  106 

thiosulphuric,  106 

trithionic,  106 

uric,  457 

valerianic,  329 
Acidimetry,  256 
Acids,  amido-,  356 

aromatic,  369 

biliary,  441 

definitions  of,  58 

detection  of,  241 

fatty,  322 

organic,  322 

sulphonic,  321 

thio-,  324 
Aconitine,  402 
Acrolein,  344 
Actinic  waves,  27 
Adhesion,  32 
^ther,  341 
Affinity,  chemical,  39 
Agate,  97 

Air,  composition  of,  85 
Alabaster,  153 
Albumin,  412 

in  urine,  465 
Albuminates,  414 
Albuminous  substances  410 

analytical  reactions  of,  411 
Albumoses,  416 
Alcohol,  307 

absolute,  311 

amyl,  313 

analytical  reactions  of,  312 

butyl,  309 

diluted,  310 

ethyl,  309 

methyl,  309 

real,  311 

Alcoholic  liquors,  312 
Alcohols,  307 

monatomic,  309 
Aldehyde,  acetic,  315 

benz-,  376 

par-,  316 
Aldehydes,  315 
Alkali  metals,  133 
Alkalimetry,  256 


Alkaline  earths,  152 
Alkaloids,  387 

antidotes  to,  390 

cadaveric,  405 

detection  of,  390 
Allotropic  modifications,  66 
Alloy,  definition  of,  133 
Allyl-mustard  oil,  355 

sulphide,  355 
Alum,  160 
Aluminum,  159 

and  ammonium  sulphate,  161 

and  potassium  sulphate,  161 

analytical  reactions  of,  164 

chloride,  162 

hydroxide,  161 

oxide,  162 

sulphate,  162 
Amalgam,  133 

ammonium,  146 

tin-,  218 
Amber,  374 
Amides,  356 
Amido-acetic  acid,  357 

-acids,  357 

-formic  acid,  357 
Amine,  diphenyl-,  383 

ethyl-,  408 

methyl  ,408 

propyl-,  408 
Amines,  356 
Ammonia,  86 

liniment,  346 

water,  87 

Ammoniated  mercury,  202 
Ammonio-copper  compounds,  189 
Ammonium,  146 

acetate,  328 

amalgam,  147 

analytical  reactions  of,  148 

benzoate,  376 

bromide,  148 

carbamate,  147 

carbonate,  147 

chloride,  147 

hydroxide,  86 

iodide,  148 

molybdate,  220 

nitrate,  148 

phosphate,  148 

sulphate,  148 

sulphide,  148 

sulphydrate,  148 

valerianate,  330 
Amorphism,  19 
Amorphous  phosphorus,  110 
Amygdalin,  376 
Amyl  alcohol,  313 

nitrite,  343 
Amylene  hydrate,  313 
Amyloid,  353 

substance,  416 
Amylopsin,  418,  443 
Analysis,  definition  of,  57 


INDEX. 


489 


Analysis  elementary,  277 
gas-,  270 
gravimetric,  250 
organic,  277 
proximate,  280 
qualitative,  222 
quantitative,  249 
ultimate,  280 
urinary,  449 
volumetric,  249 
Analytical  chemistry,  222 

reactions  of  acetanilid,  383 

acetates,  327 

alcohol,  312 

albuminous  substances,  411 

aluminum,  164 

ammonium,  148 

antifebrine,  383 

antimony,  215 

antipyrine,  385 

arsenic,  209 

atropine,  400 

barium,  158 

benzoates,  376 

bile,  440 

bismuth,  191 

blood,  431 

borates,  99 

bromides,  124 

brucine,  400 

calcium,  156 

carbolic  acid,  369 

carbon,  92 

carbonates,  ,95 

cerium,  164 

chloral,  317 

chlorates,  122 

chlorides,  120 

chloroform,  319 

cholesterin,  442 

chromates,  179 

chromium,  179 

citrates,  337 

cobalt,  184 

cocaine,  402 

codeine,  395 

copper,  190 

cyanides,  361 

ferric  salts,  173 

ferricyanides,  363 

ferrocyanides,  363 

ferrous  salts,  173 

fluorides,  126 

gastric  juice,  434 

glycerin,  313 

gold,  219 

grape-sugar,  348 

hippuric  acid,  458 

hydriodic  acid,  125 

hydrobromic  acid,  123 

hydrochloric  acid,  120 

hydrocyanic  acid,  361 

hypochlorites,  122 

hypophosphites,  115 


Analytical  reactions  of  iodides,  125 

iron,  173 

lead,  187 

lithium,  149 

magnesium,  151 

manganese,  175 

mercury,  202 

morphine,  394 

nickel,  184 

nitrates,  91 

nitrites,  89 

oxalates,  332 

phosphates,  114 

phosphites,  112 

physostigmine,  404 

platinum,  221 

potassium,  139 

pyrogallol,  379 

quinine,  398 

salicylic  acid,  377 

santonin,  381 

silicates,  98 

silver,  196 

sodium,  144 

starch,  351 

strontium,  157 

strychnine,  399 

sugar,  348 

sulphates,  105 

sulphides,  107 

sulphites,  103 

tannic  acid,  379 

tartrates,  334 

thiosulp  hates,  106 

tin,  218 

urates,  458 

urea,  455 

veratrine,  403 

zinc,  184 
Anilid,  383 
Aniline,  382 

dyes,  382 
Animal  charcoal,  156 

fluids  and  tissues,  429 
food,  422 
Anisidin,  372 
Anthracite  coal,  303 
Antidotes  to  acids,  91 
alkalies,  136 
alkaloids,  390 
antimony,  217 
arsenic,  214 
barium,  158 
carbolic  acid,  371 
copper,  189 
cyanides,  361 
hydrocyanic  acid,  361 
lead,  187 
mercury,  203 
nitric  acid,  91 
oxalic  acid,  332 
phosphorus,  111 
silver,  195 
sulphuric  acid,  105 


490 


INDEX. 


Antidotes  to  zinc,  182 
Antifebrine,  383 
Antimonous  chloride,  216 

oxide,  216 
Antimony,  215 

analytical  reactions  of,  217 

and  potassium  tartrate,  335 

antidotes  to,  217 

black,  215 

butter,  216 

chloride,  216 

crude,  215 

oxide,  216 

pentasulphide,  216 

potassium  tartrate,  216,  335 

sulphide,  215 

sulphurated,  215 

trisulphide,  215 
Antipyrine,  384 
Antiseptics,  294 
Antitoxins,  410 
Apatite,  153 
Apomorphine,  394 
Aqua  regia,  121 
Arabic  acid,  352 
Argentum,  193 
Argol,  333 
Aromatic  acids,  369 

compounds,  364 
Arrack,  313 
Arsenates,  207 
Arsenic,  205 

acid,  206 

analytical  reactions  of,  209 

antidotes  to,  214 

detection  of,   in  case  of  poisoning, 
213 

oxide,  207 

sulphides,  208 
Arsenetted  hydrogen,  208 
Arsenous  acid,  206 

anhydride,  206 

iodide,  209 

oxide,  206 
Arsine,  208 
Artiads,  47 
Asbestos,  150 
Ash,  bone,  155 

soda,  142 
Asphalt,  374 
Atmospheric  air,  85 

pressure,  31 
Atom,  definition  of,  40 
Atomic  theory,  40 

weights,  determination  of,  41,  48 
Atoms,  39 

quantivalence  of,  45 
Atropine,  400 

analytical  reactions  of,  400 
Auric  chloride,  219 

sulphide,  219 
Auripigment,  205 
Aurum,  219 
Avogadro's  law,  24 


BALSAM  copaiva,  374 
Balsams,  373 
Barite,  158 
Barium,  158 

analytical  reactions  of,  158 

antidotes  to,  158 

carbonate,  158 

chloride,  158 

chromate,  178 

dioxide,  158 

oxide,  158 

sulphate,  158 
Barometer,  30 
Basalt,  97,  159 
Bases,  definition  of,  58 
Beer,  312 
Beet-sugar,  350 
Bell-metal,  188 
Benzaldehyde,  376 
Benzene,  367 

series,  364 
Benzin,  304 
Benzol,  367 
Benzoic  acid,  375 

sulphinide,  385 
Benzyl-glycocol,  458 
Berberine,  404 
Beryllium,  61 
Bettendorff's  test,  211 
Bicarbonate  of  potassium,  147 

sodium,  143 

Bichloride  of  mercury,  199 
Bichromate  of  potassium,  177 
Bile,  440 

detection  of,  in  urine,  474 
Biliary  acids,  441 

calculi,  442 

pigments,  441 
Bilirubin,  441 
Biliverdin,  441 
Bismuth,  191 

analytical  reactions  of,  192 

carbonate,  192 

citrate,  337 

hydroxide.  192 

iodide,  191 

nitrate,  191 

oxide,  191 

oxy-salts,  191 

subcarbonate,  192 

subnitrate,  191 

sulphate,  191 

sulphide,  192 
Bismuthyl,  191 

carbonate,  191 

iodide,  191 

nitrate,  191 

Bisulphide  of  carbon,  108 
Biuret,  455 

reaction,  412 
Black  antimony,  215 

-ash,  142 

-lead,  92 

oxide  of  copper,  188 


INDEX. 


491 


Black  oxide  of  manganese,  174 
mercury,  197 

-wash,  198 

Bleaching-powder,  156 
Blood,  431 

corpuscles,  431 

detection  of,  431,  459 

-fibrin,  415 

-serum,  429 

Blood-stains,  examination  of,  433 
Blue  mass,  197 

pill,  197 

Prussian,  363 

-stone,  189 

Turnbull's,  364 

vitriol,  189 
Bone,  443 

-ash,  155 

-black,  155 

-oil,  382 
Boric  acid,  98 

analytical  reactions  of,  99 
Borax,  145 

bead,  230 
Boron,  98 

Botger's  bismuth-test,  471 
Brain,  445 
Brandy,  313 
Brass,  188 
Brittleness,  20 
Bromates,  124 

Bromides,  analytical  reactions  of,  124 
Bromine,  123 
Bromoform,  320 
Bronze,  188 
Brucine,  400 
Burettes,  253 
Butter,  448 

-milk,  448 

of  antimony,  216 


405 


p ADAVEKIC  alkaloids, 
V     Cadaverine,  408 
Cadmium,  183 

iodide,  183 

sulphate,  183 

sulphide,  183 
Caesium,  61 
Caffeine,  404 
Calamine,  180 
Calcined  magnesia,  151 
Calcium,  152 

analytical  reactions  of,  156 

bromide,  156 

carbonate,  154 

chloride,  156 

fluoride,  127 

hydroxide,  154 

hypochlorite,  156 

hypophosphite,  156 

oxalate,  332 

oxide,  153 

phosphate,  155 


Calcium  sulphate,  154 

superphosphate,  155 

tartrate,  333 
Calc-spar,  153 
Calculi,  biliary,  442 

urinary,  478 
Calomel,  198 
Camphor,  375 

-mint,  375 

Camphor,  monobromated,  375 
Cane-sugar,  350 
Caoutchouc,  374 
Capillary  attraction,  33 
Caramel,  349 
Carbamide,  357,  443 
Carbazotic  acid,  371 
Carbohydrates,  347 
Carbolic  acid,  369 

analytical  reactions  of,  370 
antidotes  to,  370 
Carbon,  92 

bisulphide,  108 

dioxide,  93 

disulphide,  108 

monoxide,  95 

Carbonate,  analytical  reactions  of,  95 
Carbonic  acid,  95 

oxide,  95 
Carbonyl,  322 
Carboxyl,  322 
Casein,  415 

vegetable,  407 
Cast-iron,  167 
Casts,  urinary,  480 
Caustic,  195 

lunar,  195 

potash,  136 
Celestite,  157 
Celluloid,  353 
Cellulose,  353 

nitro-,  353 
Cement,  444 

Centigrade  thermometer,  27 
Cerebrin,  445 
Cerite,  164 
Cerium,  164 

oxalate,  164 
Chains,  286 
Chalk,  153 
Charcoal,  92 

animal,  156 
Cheese,  448 
Chemical  action,  definition  of,  39 

affinity,  39 

divisibility,  37 

equations,  67 

formulas,  41 

reactions,  57 

symbol,  definition  of,  41 
Chemistry,  analytical,  222 

definition  of,  40 

how  to  study  it,  69 

organic,  277 

physiological,  420 


492 


INDEX. 


Chili  saltpetre,  145 
Chloral,  316 

amide,  356 

form  amide,  356 

hydrate,  317 

Chlorates,  analytical  reactions  of,  122 
Chloric  acid,  122 

oxides,  121 

Chlorides,  analytical  reactions  of,  120 
Chlorinated  lime,  156 
Chlorine,  117 

acids,  122 

oxides,  121 

water,  119 
Chloroform,  318 
Chlorous  oxide,  121 

tetroxide,  122 
Choke-damp,  96 
Cholesterin,  346,  442 
Cholic  acid,  441 
Choline,  408 

Chromates,  analytical  reactions  of,  179 
Chrome-alum,  179 

-iron  ore,  177 

-yellow,  187 
Chromic  acid,  178 

hydroxide,  178 

oxide,  178 
Chromite,  177 
Chromium,  177 

chloride,  179 

sulphate,  179 
Chyle,  429,  433 
Chyme,  425 

Cinchona  alkaloids,  398 
Cinchonidine,  399 
Cinchonine,  398 

sulphate,  398 
Cinnabar,  195,  201 
Citrates,  analytical  reactions  of,  337 
Citric  acid,  336 
Clay,  1(53 
Clot,  432 
Coagulation,  411 
Coal,  302 

-oil,  303 

-tar,  306 
Cobalt,  180 
Cocaine,  392 
Codamine,  391 
Codeine,  391 
Cognac,  313 
Cohesion,  18 
Coke,  305 
Colchicine.  392 
Collagen,  419 
Collidine,  386 
Collodion,  353 
Colloids,  35 
Colocynthin,  354 
Colophony,  373 
Columbium,  61 
Combustion,  76 
Common  salt,  141 


Compound  radicals,  60 
Compounds,  decomposition  of,  53 

definition  of,  38 
Congo  paper,  436 
Coniine,  391 
Copaiva  balsam,  374 
Copper,  187 

acetate,  328 

ammonio-sulphate,  189 

analytical  reactions  of,  190 

antidotes  to,  189 

arsenite,  190 

black  oxide,  188 

-glance,  188 

hydroxide,  188 

oxide,  188 

pyrites,  188 

sulphate,  189 

sulphide,  188,  190 
Copperas,  171 
Corrosive  chloride  of  mercury,  199 

sublimate,  199 
Corundum,  160 
Cream,  448 

of  tartar,  334 
Creamo meter,  450 
Creosote,  370 
Crude  antimony,  215 

sulphur,  100 

tartar,  333 
Cryptopine,  391 
Crystallin,  414 
Crystallization,  18 
Crystalloids,  35 
Cubic  nitre,  145 
Cumene,  366 
Cupric  acetate,  323 

arsenite,  190 

ferrocyanide,  190 

hydroxide,  188 

oxide,  188 

sulphate,  189 

sulphide,  187, 190 

tar tr ate,  471 
Cuprous  oxide,  188 
Cuprum,  187 
Curd,  447 

Cyanhydric  acid,  358 
Cyanic  acid,  362 
Cyanides,  analytical  reactions  of,  361 

antidotes  to,  361 
Cyanogen,  358 
Cymene,  372 
Cystin,  480 


D ALTON'S  atomic  theory,  43 
Decay,  291 

Decomposition  by  electricity,  54 
heat,  37,  53 
light,  54 

various  modes  of,  53 
Decrepitation,  228 
Deflagration,  229 


INDEX. 


493 


Dentine,  444 
Deodorizers,  294 

Detection  of  impurities  in  official  prep- 
arations, 271 
Deposits,  urinary,  477 
Derivatives,  289 
Desiccator,  251 
Destructive  distillation,  290 
Dextrin,  352 
Dextrose,  348 
Diacetic  ether,  384 
Dialysis,  35 
Dialyzed  iron,  170 
Diamond,  92 
Diastase,  351 
Diazo-reaction,  476 
Dibasic  acids,  58,  331 
Dicyanogen,  358 
Didymium,  61 
Diffusion,  34 
Digatalein,  354 
Digital  in,  354 
Digitonin,  354 
Digitoxin,  354 
Digestion,  424 
Dimorphism,  19 
Diphenyl-amine,  383 
Disinfectants,  294 
Distillation,  26 

destructive,  290 

dry,  290 

fractional,  299 
Disulphide  of  carbon,  108 
Divisibility,  21 

chemical,  37 
Dolomite,  150 
Donovan's  solution,  209 
Double  salts,  60 
Dried  alum,  161 
Drinking  water,  81 
Dry  distillation,  290 
Drying-oven,  250 
Ductility,  20 
Dynamite,  314 


EARTHS,  160 
alkaline,  152 
Ebonite,  374 
Ecgonine,  402 
Elasticity,  20 
Elaterin,  355 
Electricity,  54 
Elementary  analysis,  277 
Element,  definition  of,  38 
Elements,  61 

derivation  of  names  of,  71, 129 

natural  'groups  of,  62 

non-metallic,  72 

metallic,  128 

relative  importance  of,  60 

time  of  discovery  of,  72,  131 

valence  of,  72 
Emerald  green,  329 


Emery,  160 

Empirical  formulas,  283 
Emulsine,  376 
Enamel,  444 
Energy,  18 
Enzymes,  418 
Epithelium,  444 
Epsorn  salt,  151 
Equations,  chemical,  67 
Equivalence,  47 
Erbium,  61 
Eserine,  404 
Essential  oils,  306 
Esters,  339 
Ethane,  300 
Ethene,  96,  305 
Ether,  339 

acetic,  343 

diacetic,  384 

ethyl,  341 

nitrous,  343 

sulphuric,  341 
Ethers,  339 
Ethyl,  310 

acetate,  343 

alcohol,  310 

bromide,  321 

ether,  341 

hydroxide,  310 

hydride,  300 

nitrite,  343 

oxide,  343 
Ethylene,  306 
Ethylic  alcohol,  309 
Eucalyptol,  375 
Extension,  17 


]?AHKENHEIT'S  thermometer,  27 

F     Fatty  acids,  324 

Fats,  344 

Feathers,  444 

Feces,  443 

Fehling's  solution,  471 

Feldspar,  135,  160 

Fermentation,  292 

Ferments,  293,  418 

Ferric  acetate,  328 

chloride,  169 

citrate,  337 

hydrate,  168 

hydroxide,  168 

hypophosphite,  174 

nitrate,  172 

oxide,  169 

salts,  analytical  reactions  of,  173 

sulphate,  171 

sulphocyanate,  172 

tartrate,  336 

valerian  ate,  330 
Ferricyanogen,  362 

Ferricyanides,  analytical  reactions  of,  363 
Ferrocyanides,  analytical  reactions  of,  363 
Ferrocyanogen,  362 


494 


INDEX. 


Ferrous  bromide,  171 

carbonate,  172 

chloride,  169 

-ferric  oxide,  168 

hydroxide,  168 

iodide,  170 

^ctate,  338 

oxalate,  332 

oxide,  168 

phosphate,  172 

salts,  analytical  reactions  of,  173 

sulphate,  171 

sulphide,  171 
Ferrum,  167 
Fibrin,  415 

vegetable,  416 
Fibrinogen,  414 
Fire-damp,  96,  301 
Flame,  structure  of,  97 

-tests,  230 

Fleitmann's  test,  211 
Flowers  of  sulphur,  100 
Fluorine,  126 
Fluorspar,  126 
Food,  absorption  of,  426 

animal,  422 

nitrogenous,  423 

plant,  421 

Force,  definition  of,  18 
Formamide,  356 
Formic  acid,  325 
Formulas,  chemical,  41 

empirical,  283 

graphic,  285 

molecular,  283 

rational,  285 
Fowler's  solution,  207 
Fractional  distillation,  299 
Fruit-sugar,  349 
Fusel  oil,  313 
Fusibility  of  metals,  129 


pALENA,  185 

VJ     argentiferous,  193 

Gallic  acid,  379 

Gallium,  61 

Gall-stones,  442 

Galvanized  iron,  181 

Gas-analysis,  270 
definition  of,  20 
-furnace,  281 
illuminating,  305 

Gasoline,  304 

Gastric  juice,  429,  434 

Gay  Lussac's  burette,  254 
law,  44 

Gelatin,  419 

Gelatinized  starch,  352 

Gelatinoids,  419 

Germanium,  61 

German  silver,  188 

Gin,  313 

Glacial  acetic  acid,  327 


Glacial  phosphoric  acid,  113 

Glass,  163 

Glauber's  salt,  143 

Globulin,  413 

Glucinum,  61 

Glucose,  348 

Glucosides,  354 

Glue,  433 

Gluten,  416 

Glycerides,  345 

Glycerin,  313 

Glycerites,  313 

Glycine,  357 

Glycocoll,  357,  431 

Glycocolic  acid,  441 

Glycogen,  354 

Glycols,  307 

Glycozone,  83 

Glycyrrhizin,  354 

Gmelin's  test,  441 

Gold,  219 

and  sodium  chloride,  219 

analytical  reactions  of,  219 

chloride,  219 

coin,  219 

sulphide,  219 

Golden  sulphuret  of  antimony,  216 
Goulard's  extract,  328 
Graham's  law,  36 
Granite,  160 
Grape-sugar,  348 
Graphic  formulas,  285 
Graphite,  92 

Gravimetric  methods,  250 
Gravitation,  28 
Green  vitriol,  171 
Guaranin,  404 
Gum,  352 

-arabic,  352 

British,  352 

-resins,  372 
Gun-cotton,  353 

-metal,  188 
Gunpowder,  138 
Gutta-percha,  374 
Gypsum,  153 


HAIR,  444 
Hsematin,  417 
Hsemato-crystallin,  417 
Hsemine,  417 

crystals,  433,  480 
Haemoglobin,  417 
Halogens,  117 
Haloids,  117 
Hardness,  19 
Heat,  24 

action  upon  compounds,  53 
matter   21 

organic  substances,  286 
decomposition  by,  37,  55 
latent,  25 
specific,  27 


INDEX. 


495 


Heavy  magnesia,  151 

spar,  158 
Helleborin,  354 
Hematite,  166 
Hepar,  106,  137 
Hippuric  acid,  458 
Homologous  series,  287 
Hoofs,  444 
Hornblende,  160 
Horns,  444 
Humus,  428 
Hydrargyrum,  196 
Hydrastine,  403 
Hydrastinine,  403 
Hydriodic  acid,  125 
Hydrobromic  acid,  123 
Hydrocarbons,  96,  298 
Hydrochloric  acid,  120 

analytical  reactions  of,  120 
Hydrocyanic  acid,  358 

analytical  reactions  of,  361 
antidotes  to,  361 
Hydroferricyanic  acid,  362 
Hydroferrocyanic  acid,  362 
Hydrofluoric  acid,  127 
Hydrogen,  78 

arsenide,  208 

arsenetted,  208 

dioxide,  83 

fluoride,  127 

peroxide,  83 

phosphide,  116 

phosphoretted,  116 

sulphide,  107,  235 

sulphuretted,  107 
Hydrometers,  29 
Hydrosulphuric  acid,  107 
Hydroxyl,  296 
Hygrine,  402 
Hyoscine,  401 
Hyoscyamine,  401 
Hypobromites,  124 
Hypochlorites,  tests  for,  122 
Hypochlorous  acid,  122 

oxide,  121 

Hyponitrous  acid,  89 
Hypophosphites,  tests  for,  116 
Hypophosphorous  acid,  115 
Hyposulphurous  acid,  106 


TCHTHYOL,  371 

1     Illuminating  gas,  305 

oil,  304 

Impurities,  detection  of,  271 
Indestructibility,  36 
India-rubber,  374 
Indican,  354,460 
Indicators,  256 
Indigo-red,  460 
Indium,  61 
Indol,  443 
Inosite,  349 
Iodides,  analytical  reactions  of,  126 


lodimetry,  264 
Iodine,  125 

tests  for  it,  126 

tincture  of,  125 
Iodized  starch,  352 
lodoform,  320 
lodol,  386 
Iridium,  61 
Iron,  165 

acetate,  328 

analytical  reactions  of,  173 

bromide,  171 

carbonate,  172 

cast-,  167 

chlorides,  169 

citrate,  337 

dialyzed,  170 

galvanized,  181 

hydroxides,  168 

hypophosphite,  174 

iodide,  170 

lactate,  338 

nitrate,  172 

ores,  166 

oxalates,  332 

oxides,  168 

phosphates,  172 

pig,  167 

pyrites,  166 

reduced,  167 

scale  compounds  of,  336 

sulphates,  171 

sulphide,  171 

tannate,  173 

tartrate,  336 

trioxide,  169 

wrought-,  167 
Isomerism,  289 
Isomorphism,  19 


KAIKINE,  387 
Kalium,  134 
Kelp,  125 
Keratin,  444 
Ketones,  329 
Kreatin,  445 


[  ACTIC  acid,  338 
LJ     Lactometer,  449 
Lactoscope,  450 
Lactose,  351 
Lanolin,  346 
Lanthanum,  61 
Lapis  infernalis,  195 

lazuli,  163 
Lardacein,  416 
Latent  heat,  25 
Laudamine,  391 
Laudanosine,  391 
Laughing-gas,  88 
T-aurinol,  375 
Law,  Avogadro's,  24 


496 


INDEX. 


Law,  Charles's,  25 

of  chemical  combination  by  volume, 44 
by  weight,  42 

of  the  conservation  of  energy,  36 

of  constancy  of  composition,  42 

of  diffusion  of  gases,  36 

Dulong  and  Petit,  51 

of  equivalents,  45 

Gay  Lussac's,  44 

Graham's,  36 

Mariotte's,  20 

Mendelejeff's,  62 

of  multiple  proportions,  43 

Newton's,  28 

periodic,  62 

of  Eaoult,  52 
Lead,  185 

acetate,  328 

analytical  reactions  of,  187 

antidotes  to,  187 

carbonate,  186 

chloride,  185 

chromate,  186 

iodide,  186 

nitrate,  186 

oleate,  346 

oxide,  185 

phosphate,  185 

plaster,  346 

sugar  of,  328 

-water,  328 

white,  186 
Lecithin,  442 
Legumin,  415 
Leucomaines,  409 
Levulose,  349 
Liebig's  condenser,  311 
Light,  decomposition  by,  54 

magnesia,  150 
Lignine,  353 
Lignite,  303 
Lime,  acid  phosphate  of,  155 

chloride  of,  156 

chlorinated,  156 

-kiln,  153 

liniment,  346 

quick-,  153 

slaked,  154 

superphosphate  of,  155 

-water,  154 
Limestone,  153 
Liniments,  346 
Liquefaction  of  solids,  231 
Liquids,  definition  of,  20 
Litharge,  185 
Lithium,  146 

benzoate,  376 

bromide,  146 

carbonate,  146 

citrate,  337 

salicylate,  377 
Litmus,  58 

solution,  256 
Lunar  caustic,  195 


Lutidine,  386 
Lymph,  434 


MAGNESIA,  150 
calcined,  151 
Magnesite,  150 
Magnesium,  150 

analytical  reactions  of,  152 

carbonate,  151 

citrate,  337 

oxide,  151 

sulphate,  151 

sulphite,  151 
Magnetic  iron  ore,  166 
Malachite,  188 
Malic  acid,  333 
Malleability,  20 
Maltose,  351 
Manganates,  175 
Manganese,  174 

analytical  reactions  of,  176 

black  oxide  of,  174 

dioxide,  174 

oxides  of,  174 
Manganous  carbonate,  175 

hydroxide,  175 

oxide,  174 

sulphate,  175 
Mannitose,  349 
Marble,  153 
Mariotte's  law,  20 
Marsh-gas,  96,  301 
Marsh's  test,  212 
Mass,  17 

-action,  56 
Massicot,  185 
Mastication,  425 
Matter,  definition  of,  17 
Mayer's  solution,  389 
Meconic  acid,  395 
Meconidine,  391 
Meerschaum,  150 
Melissic  acid,  325 
Melitose,  351 

Melting-points  of  metals,  131 
Mendelejeff's  law,  62 
Menthol,  375 
Mercaptans,  309 
Mercurial  ointment,  197 

plaster,  197 
Mercuric  chloride,  199 

cyanide,  361 

fulminate,  364 

iodide,  200 

nitrate,  201 

oxide,  198 

salts,  analytical  reactions  of,  202 

sulphate,  200 

sulphide,  201 
Mercurous  chloride,  198 

chromate,  179 

iodide,  200 

nitrate,  201 


INDEX. 


497 


Mercurous  oxide,  197 

salts,  analytical  reactions  of,  202 

sulphate,  "201 

sulphide,  201 
Mercury,  196 

ammoniated,  202 

analytical  reactions  of,  202 

antidotes  to,  203 

basic  sulphate,  201 

carbonates,  203 

chlorides,  198,  199 

iodides,  200 

nitrates,  201 

oleate,  330 

oxides,  198 

sulphates,  200 

sulphides,  201 

with  chalk,  197 
Metaldehyde,  316 
Metallic  elements,  129 
Metallo-cyanides,  362 
Metalloids,  71 
Metals,  129 

classification  of,  133 

derivation  of  names,  129 

melting-points  130 

separation  of,  233 

specific  gravity,  131 

valence,  132 
Metamerism,  289 
Metaphosphoric  acid,  113 
Methane,  96,  301 

series,  300 
Methyl  alcohol,  309 

amine,  408 

hydride,  300 

hydroxide,  309 

orange,  256 
Mica,  160 

Microcosmic  salt,  226 
Milk,  445 

adulterations  of,  449 

analysis  of,  450 

-casein,  448 

of  sulphur,  101 

-sugar,  351 
Millard's  test,  467 
Millon's  reagent,  412 
Mineral  waters,  81 
Minium,  186 
Mint-camphor,  375 
Mispickel,  205 
Molasses,  350 
Molecular  motion,  24,  27 

theory,  22 

weight,  41,  51 
Molecule,  definition  of,  22 
Molybdenum,  220 
Molybdic  acid,  220 

oxide,  220 
Monobasic  acids,  58 
Monsel's  solution,  172 
Morphine,  393 

acetate,  394 


Morphine,  analytical  reactions  of,  394 

hydrochlorate,  394 

sulphate,  394 
Muscle-sugar,  349 
Muscles,  445 

Mucilage  of  starch,  264,  352 
Mucin,  445 
Mucus,  445 
Murexid  test,  457 
Muriatic  acid,  120 
Myosin,  414 
Myronic  acid,  354 
My  rosin,  354 


NAILS,  444 
Naphtalin,  380 
JSTaphtol,  380 

beta-,  381 
Narceine,  391 
Narcotine,  391 
Nascent  state,  57 
Natrium,  141 
Nessler's  solution,  225 
Neutral  substances,  58 
Newton's  law,  28 
Nickel,  180 
Nicotine,  391 
Niobium,  61 

Nitrates,  analytical  reactions  of,  91 
Nitre,  137 
Nitric  acid,  89 
Nitro-benzene,367 

-cellulose,  353 

-cyan-methane,  364 

-glycerin,  314 
Nitrogen,  84 

determination,  282 

oxides,  88 
Nitro-hydrochloric  acid,  121 

-muriatic  acid,  120 
Nitrous  acid,  89 

ether,  343 

oxide,  88 
Nomenclature,  66 
Non-metallic  elements,  71 
Nordhausen  sulphuric  acid,  106 
Normal  solutions,  254 
Nutrition  of  animals,  424 
Ny lander's  reagent,  472 


0 


IL,  almond,  345 
bitter  almond,  376 
bone,  386 
castor,  345 
cod-liver,  345 
cotton-seed,  345 
heavy,  367 
illuminating,  304 
juniper,  289 
lemon,  289 
light,  367 
linseed,  345 


32 


498 


INDEX. 


Oil,  olive,  345 

turpentine,  373 

vitriol,  103 

wintergreen,  377 
Oils,  essential,  306 

fat,  344 

Olefiant  gas,  306 
Olefines,  306 
Oleic  acid,  330 
Oleo-resins,  373 
Olive  oil,  345 
Opium,  392 

-alkaloids,  391 

deodorized,  392 
Organic  analysis,  280 

chemistry,  277 

substances,  classification  of,  296 
decomposition  of,  290 
formation  of,  in  plants,  421 
Orpiment,  205 
Orthophosphoric  acid,  113 
Osmium,  61 
Osmose,  35 
Ossein,  419 

Oxalates,  analytical  reactions  of,  332 
Oxalic  acid,  331 

antidotes  to,  332 
Oxide,  definition  of,  76 
Oxidimetry,  260 
Oxygen,  73 
Ozone,  77 


PALLADIUM,  61 

I      Palmitic  acid,  325 

Palmitin,  344 

Pancreatic  juice,  443 

Pancreatin,  419 

Papaverine,  391 

Paper,  353 

Paraglobulin,  413 

Parafiin,  303 

Paraldehyde-  316 

Paris  green,  329 

Pearl-white,  192 

Peat,  303 

Pepsin,  418,  435 

saccharated,  418 

Peptone,  416 

Perchloric  acid,  122 

Periodic  law,  62 

Perissads,  47 

Permanganates,  175 

Petrolatum,  304 

Petroleum,  303 
-ether,  304 

Pettenkofer's  test,  441,  475 

Phenacetine,  372 

Phenetidin,  372 

Phenol,  369 

methyl-propyl,  375 
phthalein,  256,  378 
sulphonic  acid,  371 
trinitro,  371 


Phenyl-acetamide,  383 

-arnine,  382 

hydrazine,  384 

hydrate,  369 

salicylate,  378 

Phosphates,  analytical  reactions  of,  115 
Phosphine,  116 

Phosphites,  analytical  reactions  of,  113 
Phospho-molybdic  acid,  389 
Phosphoretted  hydrogen,  116 
Phosphoric  acid,  113 
Phosphorous  acid,  112 
Phosphorus,  108 

antidotes  to,  111 

detection  of,  111 

determination  in  organic  compounds, 
286 

red  or  amorphous,  110 
Phtalic  acid,  378 
Physiological  chemistry,  420 
Physostigmine,  404 
Picoline,  386 
Picric  acid,  371 
Picrotoxin.  355 
Pilocarpine,  404 
Piperin,  405 
Pipettes,  253 
Plant-fibre,  353 

-food,  420 

Plaster-of-Paris,  154 
Platinic  chloride,  220 
Platinum,  220 

and  ammonium  chloride,  220 

and  potassium  chloride,  220 
Plumbago,  92 
Plumbum,  185 
Polymerism,  290 
Polymorphism,  19 
Porcelain,  163 
Porosity,  32 
Port  wine,  312 
Porter,  312 
Potash,  135 

caustic,  136 
Potassium,  134 

acetate,  328 

acid  carbonate,  138 

acid  oxalate,  332 

acid  tartrate,  334 

analytical  reactions  of,  140 

bicarbonate,  137 

bichromate,  177 

bitartrate,  334 

bromide,  140 

carbonate,  137 

chlorate,  138 

chromate,  177 

citrate,  337 

cyanate,  360 

cyanide,  360 

dichromate,  177 

ferricyanide,  364 

ferrocyanide,  363 

hydrate,  136 


INDEX. 


499 


Potassium  hydroxide,  136 

hypophosphite,  139 

iodide,  139 

manganate,  175 

nitrate,  137 

oxalate,  332 

permanganate,  175 

prussiate,  363 

sodium  tartrate,  335 

sulphate,  138 

sulphite,  139 

sulphocyanate,  362 

sulphurated,  139 

tartrate,  334 
Preliminary  examination,  227 

table  for,  232 
Proof-spirit,  311 
Propionic  acid,  324 
Propyl  alcohol,  313 
Proteids,  410 

bacterial,  409 
Protopine,  391 
Prussian  blue,  363 
Prussiate  of  potash,  red,  363 

yellow,  363 
Prussic  acid,  358 
Pseudo-morphine,  391 
Ptomaines,  405 
Ptyalin,  434 
Putrefaction,  292 
Pyridine,  386 
Pyrites,  copper,  188 

iron,  166 
Pyrogallol,  379 
Pyrolusite,  174 
Pyrophosphoric  acid,  113 
Pyroxylin,  353 
Pyrrole,  386 


AUANTIVALENCE,  45 
\l     Quartz,  97 
Quicksilver,  196 
Quinidine,  398 
Quinine,  397 

acid  sulphate,  397 

analytical  reactions  of,  ! 

citrate  of  iron  and,  397 

sulphate,  397 

valerianate,  330 
Quinoline,  387 


RADICAL,  definition  of,  60,  286 
Reactions,  57 
analytical,  58 
synthetical,  58 
Keagents,  list  of,  225 
Realgar,  205 

Red  iodide  of  mercury,  200 
lead,  186 

oxide  of  copper,  188 
oxide  of  mercury,  198 
phospnorus   110 


Red  precipitate,  198 
Reinsch's  test,  211 
Rennet,  435 

Residue,  definition  of,  60,  286 
Resin,  373 
Resorcin,  372 
Respiration,  94,  427 
Rhodium,  61 
Rochelle  salt,  335 
Rock-crystal,  97 

-salt,  141 
Rosaniline,  383 
Rosin,  373 
Rosolic  acid,  256 
Rubber,  374 
Rubidium,  61 
Ruby,  160 
Rum,  313 
Ruthenium,  61 


C  ACCHARINE,  385 
U    Saccharose,  352 
Salicin,  378 
Salicylic  acid,  377 
Saliva,  434 
Salol,  378 
Sal-ammoniac,  146 

sodae,  142 
Salt  cake,  142 

common,  141 
Saltpetre,  137 

Chili,  145 
Salts,  definition  of,  59 

tables  of  solubility,  246,  248 
Sand,  97 
Santonin,  381 
Sapphire,  160 
Sarkin,  445 

Scale  compounds  of  iron,  336 
Scandium,  61 
Scheele's  green,  210 
Schweinfurth's  green,  210,  326 
Seidlitz  powder,  335 
Selenium,  108 
Serpentine,  150 
Serum,  431 
Sherry  wine,  312 
Silica,  97 
Silicates,  98 
Silicic  acid,  98 
Silicium,  97 
Silicon,  97 
Silver,  193 

analytical  reactions  of,  196 

antidotes  to,  195 

chloride,  194 

chromate,  196 

cyanide,  360 

fulminate,  364 

German,  188 

iodide,  195 

nitrate,  194 

oxide,  195 


500 


INDEX. 


Silver,  sulphide,  196 

volumetric  solution,  267 
Sinigrin,  354 
Skatol,  443 
Slaked  lime,  154 
Slate,  160 
Soap,  345 
Soapstone,  150 
Soda,  142 

-ash,  142 

-lime,  281 
Sodium,  141 

acetate,  328 

analytical  reactions  of,  145 

arsenate,  207 

benzoate,  376 

bicarbonate,  143 

bisulphite,  144 

borate,  145 

bromide,  145 

carbonate,  143 

chlorate,  145 

chloride,  142 

hydrate,  142 

hydroxide,  142 

hypophosphite,  145 

hyposulphite,  144 

iodide,  145 

nitrate,  145 

phosphate,  144 

salicylate,  377 

sulphate,  143 

sulphite,  144 

sulphocarbolate,  371 

thiosulphate,  144 
Solids,  definition  of,  18 
Sparteine,  392 
Specific  heat,  27,  50 

weight,  29 
Spirit  of  hartshorn,  87 

of  mindererus,  328 

of  wine,  312 

proof,  311 

wood-,  309 

Standard  solutions,  254 
Stannic  acid,  218 

chloride,  218 

sulphide,  218 
Stannous  chloride,  218 

hydroxide,  218 

sulphide,  218 
Stannum,  218 
Starch,  351 

iodized,  352 

solution,  264 
Stearic  acid,  325 
Stearin,  344 
Stearoptenes,  374 
Steel,  167 
Steapsin,  418,  443 
Stibium,  215 
Stibnite,  215 
Strontianite,  157 
Strontium,  157 


Strontium,  analytical  reactions  of,  157 

bromide,  157 

carbonate,  157 

chloride,  157 

nitrate,  157 

sulphate,  157 
Structure  of  flame,  97 
Strychnine,  399 

analytical  reactions  of;  399 

sulphate  399 
Sublimation,  26 
Sublimed  sulphur,  100 
Substitution,  288 
Sugar,  348 

cane-,  350 

detection  of,  in  urine,  469 

fruit-,  349 

grape-,  348 

of  lead.  328 

milk,  351 

Sulphates,  analytical  reactions  of,  105 
Sulphides,  analytical  reactions  of,  107 
Sulphites,  analytical  reactions  of,  103 
Sulphocarbolates,  371 
Sulphocyanic  acid,  362 
Sulphonal,  321 
Sulphonic  acid,  321,  371 
Sulphur,  100 

determination  in  organic  compounds. 
286 

dioxide,  101 

flowers  of,  100 

milk  of,  101 

precipitated,  101 

sublimed,  100 

trioxide,  103 
Sulphurated  antimony,  215 

lime,  156 

Sulphuretted  hydrogen,  107,  235 
Sulphuric  acid,  103 

antidotes  to,  106 
dilute,  105 
fuming,  106 
Nordhausen,  106 
Sulphuric  ether,  341 
Sulphurous  acid,  102 
Superphosphate  of  lime,  155 
Surface-action,  32 
Sweet  spirit  of  nitre,  343 
Symbols,  function  of,  41 
Synthesis,  57 
Syntonin,  415 


TABLES  of  solubility,  246,  248 

1     Talc,  150 

Tannic  acid,  379 

Tannin,  379 

Tantalum,  61 

Tanret's  test,  467 

Tartar,  444 

cream  of,  334 

crude,  333 

emetic,  335 


INDEX. 


501 


Tartaric  acid  333 

Tartrates,  analytical  reactions  of,  334 

Taurine,  441 

Taurocholic  acid,  441 

Teeth,  444 

Tellurium,  108 

Tenacity,  20 

Tension,  20 

Terebene,  373 

Terpenes,  372 

Tetanine,  409 

Thalline,  387 

Thallium,  61 

Thebaine,  391 

Theine,  404 

Theobromine,  405 

Thermometers,  27 

Thorium,  61 

Thymol,  375 

Tin,  218 

-amalgam,  219 

analytical  reactions  of,  218 

chlorides  of,  218 

-plate,  218 

-stone,  218 
Titanium,  61 
Titration,  256 
Titre,  257 
Toluene,  366 
Toxalbumins,  409 
Toxines,  407 
Trichloraldehyde,  316 
Trichlormethane,  318 
Trinitro-cellulose,  353 

-phenol,  371 
Triple  phosphate,  480 
Trommer's  test,  470 
Trypsin,  425,  443 
Tungsten,  61 
Turpentine,  373 
Turpeth  mineral,  201 
Type-metal,  215 
Types,  chemical,  288 
Tyrotoxicon,  409 

ULTIMATE  analysis,  281 
Ultramarine,  163 
Ultzmann's  test,  475 
Uranium,  61 
Urates,  468 
Urea,  453 

determination  of,  455 

nitrate,  455 
Uric  acid,  457 
Urinary  calculi,  478 

sediments,  477 
Urine,  452 

analysis,  459 

color,  459 

composition,  453 

reaction,  461 

secretion,  452 

specific  gravity,  462 


Urinometer,  462 
Urochrome,  460 
Urobilin,  460 


VALENCE,  45 
Valerianates,  330 
Valerianic  acid,  329 
Vanadium,  61 
Vaseline,  304 
Veratrine,  403 

analytical  reactions  of,  403 

oleate,  330 
Verdigris,  328 
Vermilion,  202 
Vinegar,  327 
Vitellin,  414 
Vitriol,  blue,  189 

green,  171 

oil  of,  103 

white,  182 
Volatile  oils,  306 
Volumetric  analysis,  253 
Vulcanite,  374 
Vulcanized  rubber,  374 


117  ASTE  products  of  animal  life,  427 
U      Water,  81 

ammonia  in,  149 
distilled,  82 
drinking,  81 
-gas,  96 
lead-,  328 
lime-,  154 
mineral,  81 
nitric  acid  in,  91 
of  ammonia,  87 
of  bitter  almond,  376 
Wax,  340 
Weight,  29 
atomic,  40 
specific,  29 
molecular,  41,  51 
Whey,  447 
Whiskey,  313 
White  arsenic,  206 
lead,  186 
precipitate,  202 
vitriol,  182 
Wine,  312 
Witherite,  158 
Wood-naphtha,  309 

-spirit,  309 
Wrought-iron,  167 


YANTHIN,  445 
A    Xylene,  366 

YELLOW  oxide  of  mercury,  198 
1     prussiate,  363 

subsulphate  of  mercury,  201 

-wash,  198 


502 


INDEX. 


Ytterbium,  61 
Yttrium,  61 


L 


,  180 

acetate,  328 

analytical  reactions  of,  183 
antidotes  to,  182 
-blende,  180 
bromide,  182 
carbonate,  182 


Zinc  chloride,  181 
ferrocyanide,  183 
hydroxide,  181 
iodide,  182 
oxide,  181 
phosphide,  182 
sulphate,  182 
valerianate,  330 
-white,  181 

Zirconium,  61 


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CHURCHILL   (FLEET WOOD).     ESSAYS   ON  THE  PUERPERAL  FEVER. 

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CLARKE  (W.  B.)  AND  LOCKWOOD  (C.  B.).  THE  DISSECTOR'S  MANUAL. 
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CLELAND  (JOHN).  A  DIRECTORY  FOR  THE  DISSECTION  OF  THE 
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CLINICAL  MANUALS.     See  Serie*  of  Clinical  Manuals,  page  13. 

CLOUSTON  (THOMAS  S.).  CLINICAL  LECTURES  ON  MENTAL  DIS- 
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Just  ready.  Cloth,  $4.75. 

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CLOWES    (FRANK).  AN  ELEMENTARY   TREATISE    ON  PRACTICAL 

CHEMISTRY  AND  QUALITATIVE  INORGANIC  ANALYSIS.    From  the 

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COATS  (JOSEPH).  A  TREATISE  ON  PATHOLOGY.  In  one  volume  of  829 
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COLEMAN  (AIiFRED).  A  MANUAL  OF  DENTAL  SURGERY  AND  PATH- 
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CONDIE  (D.  FRANCIS).  A  PRACTICAL  TREATISE  ON  THE  DISEASES 
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CORNIL  (V.).  SYPHILIS:  ITS  MORBID  ANATOMY,  DIAGNOSIS  AND 
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CULBRETH  (DAVID  M.  R.).    MATERIA  MEDICA  AND  PHARMACOLOGY. 

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D  ALTON  (JOHN  C.)..  A  TREATISE  ON  HUMAN  PHYSIOLOGY.  Seventh 
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DU ANE  ( ALEXANDER ) .  THE  ST  U DENT'S  DICTIONAR  Y  OF  MEDICINE 
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175  pages.  Cloth,  $1.50. 

DUNGLISON  (ROBLEY).  A  DICTIONARY  OF  MEDICAL  SCIENCE.  Con- 
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lege of  Philadelphia.  Edited  by  KICHARD  J.  DUNGLISON,  A.M.,  M.D.  Twenty-first 
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EDES  (ROBERT  T.).     TEXT-BOOK  OF  THERAPEUTICS  AND  MATERIA 

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EDIS  (ARTHUR  W.).  DISEASES  OF  WOMEN.  A  Manual  for  Students  and 
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Cloth,  $3 ;  leather,  $4. 

ELLIS  (GEORGE  VINER'.  DEMONSTRATIONS  IN  ANATOMY.  Being  a 
Guide  to  the  Knowledge  of  the  Human  Body  by  Dissection.  From  the  eighth  and  revised 
English  edition.  In  one  octavo  volume  of  716  pages,  with  249  engravings.  Cloth,  $4.25; 
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ERICHSEN  (JOHN  E.).  THE  SCIENCE  AND  ART  OF  SURGERY.  A  new 
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volumes  containing  2316  pages,  with  984  engravings.  Cloth,  $9 ;  leather,  $11. 

ESSIG  (CHARLES  J.).  PROSTHETIC  DENTISTRY.  See  American  lexl-book* 
of  Dentistry,  page  2. 

FARQUHARSON  (ROBERT).  A  GUIDE  TO  THERAPEUTICS.-  Fourth 
American  from  fourth  English  edition,  revised  bv  FRANK  WOODBURY,  M.D.  In  one 
12mo.  volume  of  581  pages.  Cloth,  $2.50. 

FIELD  (GEORGE  P.).  A  MANUAL  OF  DISEASES  OF  THE  EAR.  Fourth 
edition.  In  one  octavo  volume  of  391  pages,  with  73  engravings  and  21  colored  plates. 
Cloth,  $3.75. 

FLINT  (AUSTIN).  A  TREATISE  ON  THE  PRINCIPLES  AND  PRACTICE 
OF  MEDICINE.  New  (7th)  edition,  thoroughly  revised  by  FREDERICK  P.  HENRY, 
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A  MANUAL  OF  AUSCULTATION  AND  PERCUSSION;  of  the  Physi- 
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edition,  revised  by  JAMES  C.  WILSON,  M.D.     In  one  handsome  12mo.  volume  of  274 
pages,  with  12  engravings. 

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A   PRACTICAL   TREATISE  ON  THE  PHYSICAL  EXPLORATION 

OF  THE   CHEST,  AND    THE  DIAGNOSIS  OF  DISEASES  AFFECTING 
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ume of  591  pages.     Cloth,  $4.50. 

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— , ON  PHTHISIS:  ITS  MORBID  ANATOMY,  ETIOLOGY,  ETC.    A  Series 

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FOLSOM  (C.  F.).    AN  ABSTRACT  OF  STATUTES  OF  U.  S.  ON  CUSTODY 

OF  THE  INSANE.     In  one  8vo.  volume  of  108  pages.     Cloth,  $1.50.     With  (Houston 
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FORMULARY,  THE  NATIONAL.  See  Stille,  Maisch  &  Caspar? 8  National  Dispensa- 
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FOSTER   (MICHAEL).    A    TEXT-BOOK  OF  PHYSIOLOGY.    New  (6th)  and 
revised  American  from  the  sixth  English  edition.     In  one  large  octavo  volume  of  923 
•  pages,  with  257  illustrations.     Cloth,  $4.50 ;  leather,  $5.50. 

FOTHERGILL  (J.  MILNER).  THE  PRACTITIONER'S  HAND-BOOK  OF 
TREATMENT.  Third  edition.  In  one  handsome  octavo  volume  of  664  pages. 
Cloth,  $3.75 ;  leather,  $4.75. 

POWNES  (GEORGE).  A  MANUAL  OF  ELEMENTARY  CHEMISTRY  (IN- 
ORGANIC AND  ORGANIC).  Twelfth  edition.  Embodying  WATTS'  Physical  and. 
Inorganic  Chemistry.  In  one  royal  12mo.  volume  of  1061  pages,  with  168  engravings,  and 
1  colored  plate.  Cloth,  $2.75 ;  leather,  $3.25. 

FRANKLAND  (E.)  AND  JAPP  (F.  R.).  INORGANIC  CHEMISTRY.  In  one 
Laadsome  octavo  volume  of  677  pages,  with  51  engravings  and  2  plates.  Cloth,  $3.75 ; 
leather,  $4.75. 

FULLER  (EUGENE).  DISORDERS  OF  THE  SEXUAL  ORGANS  IN  THE 
MALE.  In  one  very  handsome  octavo  volume  of  238  pages,  with  25  engravings  and 
8  full-page  plates.  Cloth,  $2.  Just  ready. 

FULLER  (HENRY).  ON  DISEASES  OF  THE  L  UNGS  AND  AIR-PASS  A  GES. 
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GIBBES  (HENEAGE).  PRACTICAL  PATHOLOGY  AND  MORBID  HIS- 
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mostly  photographic.  Cloth,  $2.75. 

GIBNEY  (V.  P.).  ORTHOPEDIC  SURGERY.  For  the  use  of  Practitioners  and 
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GOULD  (A.  PEARCE).    SURGICAL  DIAGNOSIS.    In  one  12mo.  volume  of  589 

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GRAY    (HENRY).      ANATOMY,    DESCRIPTIVE   AND   SURGICAL.      New 

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GREEN  (T.  HENRY).  AN  INTRODUCTION  TO  PATHOLOGY  AND  MOR- 
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GREENE  (WILLIAM  H.).    A  MANUAL  OF  MEDICAL  CHEMISTRY.    For 

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GROSS  (SAMUEL  D.).  A  PRACTICAL  TREATISE  ON  THE  DISEASES, 
INJURIES  AND  MALFORMATIONS  OF  THE  URINARY  BLADDER, 
THE  PROSTATE  GLAND  AND  THE  URETHRA.  Third  edition,  thoroughly 
revised  and  edited  by  SAMUEL  W.  GROSS,  M.  D.  In  one  octavo  volume  of  574  pages, 
with  170  illustrations."  Cloth,  $4.50. 

HABERSHON  (S.  0.).  ON  THE  DISEASES  OF  THE  ABDOMEN,  comprising 
those  of  the  Stomach,  (Esophagus,  Csecum,  Intestines  and  Peritoneum.  Second  Amer- 
ican from  the  third  English  edition.  In  one  octavo  volume  of  554  pages,  with  11  engrav- 
ings. Cloth,  $3.50. 

HAMILTON  (ALLAN  McL ANE ) .  NER  VO  US  DISEASES,  THEIR  DESCRIP- 
TION AND  TREATMENT.  Second  and  revised  edition.  In  one  octavo  volume  of 
598  pages,  with  72  engravings.  Cloth,  $4. 

HAMILTON  (FRANK  H.).  A  PRACTICAL  TREATISE  ON  FRACTURES 
AND  DISLOCATIONS.  Eighth  edition,  revised  and  edited  by  STEPHEN  SMITH, 
A.M.,  M.D.  In  one  handsome  octavo  volume  of  832  pages,  with  507  engravings. 
Cloth,  $o.50;  leather,  $6.50. 

HARDAWAY  (W.  A.).    MANUAL  OF  SKIN  DISEASES.     In  one  12mo.  volume 

of  440  pages.     Cloth,  $3. 

HARE  (HOBART  AMORY).  A  TEXT-BOOK  OF  PRACTICAL  THERA- 
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and  their  Employment  upon  a  Rational  Basis.  With  articles  on  various  subjects  by  well- 
known  specialists.  Fifth  and  revised  edition.  In  one  octavo  volume  of  740  pages. 
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HARE  (HOBART  AMORY),  Editor.  A  SYSTEM  OF  PRACTICAL  THERA- 
PEUTICS. By  American  and  Foreign  Authors.  In  a  series  of  contributions  by  emi- 
nent practitioners.  In  four  large  octavo  volumes  comprising  4600  pages,  with  476 
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HARTSHORNE  (HENRY).  ESSENTIALS  OF  THE  PRINCIPLES  AND 
PRACTICE  OF  MEDICINE.  Fifth  edition.  In  one  12mo.  volume,  669  pages, 
with  144  engravings.  Cloth,  $2.75 ;  half  bound,  $3. 

A   HANDBOOK  OF  ANATOMY  AND  PHYSIOLOGY.    In  one  12mo. 

volume  of  310  pages,  with  220  engravings.     Cloth,  $1.75. 

A  CONSPECTUS  OF  THE  MEDICAL  SCIENCES.     Comprising  Manuals 

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trations.    Cloth,  $4.25;  leather,  $5. 

HAYDEN  (JAMES  R.).  A  MANUAL  OF  VENEREAL  DISEASES.  In  one 
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HAYEM  (GEORGES)  AND  HARE  (H.  A.).  PHYSICAL  AND  NATURAL 
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pheric Pressure,  Climates  and  Mineral  Waters.  Edited  by  Prof.  H.  A.  HARE,  M.D. 
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HERMAN    (G.   ERNEST).    FIRST  LINES  IN  MIDWIFERY.     In  one  12mo. 

volume  of  198  pages,  with  80  engravings.     Cloth,  $1. 25.     See  Students'  Series  of  Manuals, 
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HERMANN  (L.).  EXPERIMENTAL  PHARMACOLOGY.  A  Handbook  of  the 
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HERRICK  (JAMES  B.).  A  HANDBOOK  OF  DIAGNOSIS.  In  one  handsome 
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HILL  (BERKELEY).    SYPHILIS  AND  LOCAL  CONTAGIOUS  DISORDERS. 

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HILLIER  (THOMAS).  A  HANDBOOK  OF  SKIN  DISEASES.  Second  edition. 
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HIRST  (BARTON  C.)  AND  PIERSOL  (GEORGE  A.).  HUMAN  MONSTROS- 
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HOBLYN  (RICHARD  D.).  A  DICTIONARY  OF  THE  TERMS  USED  IN 
MEDICINE  AND  THE  COLLATERAL  SCIENCES.  In  one  12mo.  volume  of 
520  double-columned  pages.  Cloth,  $1.50;  leather,  $2. 

HODGE  (HUGH  L.).  ON  DISEASES  PECULIAR  TO  WOMEN,  INCLUDING 
DISPLACEMENTS  OF  THE  UTERUS.  Second  and  revised  edition.  In  one 
8vo.  volume  of  519  pages,  with  illustrations.  Cloth,  $4.50. 

HOFFMANN  (FREDERICK)  AND  POWER  (FREDERICK  B.).  A  MANUAL 
OF  CHEMICAL  ANAL  YSIS,  as  Applied  to  the  Examination  of  Medicinal  Chemicals 
and  their  Preparations.  Third  edition,  entirely  rewritten  and  much  enlarged.  In  one 
handsome  octavo  volume  of  621  pages,  with  179  engravings.  Cloth,  $4.25. 

HOLDEN  (LUTHER).  LANDMARKS,  MEDICAL  AND  SURGICAL.  From 
the  third  English  edition.  With  additions  by  W.  W.  KEEN,  M.D.  In  one  royal  12mo. 
volume  of  148  pages.  Cloth,  $1. 

HOLMES  (TIMOTHY).  A  TREATISE  ON  SURGERY.  Its  Principles  and 
Practice.  A  new  American  from  the  fifth  English  edition.  Edited  by  T.  PICKERING 
PICK,  F.R.C.S.  In  one  handsome  octavo  volume  of  1008  pages,  with  428  engravings. 
Cloth,  $6;  leather,  $7. 

-  A  SYSTEM  OF  SURGERY.  With  notes  and  additions  by  various  American 
authors.  Edited  by  JOHN  H.  PACKARD,  M.D.  In  three  very  handsome  8vo.  volumes 
containing  3137  double-columned  pages,  with  979  engravings  and  13  lithographic  plates. 
Per  volume,  cloth,  $6  ;  leather,  $7  ;  half  Eussia,  $7.50.  For  sale  by  subscription  only. 

HORNER  (WILLIAM  E.).  SPECIAL  ANATOMY  AND  HISTOLOGY.  Eighth 
edition,  revised  and  modified.  In  two  large  8vo.  volumes  of  1007  pages,  containing  320 
engravings.  Cloth,  $6. 

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volume  of  308  pages.  Cloth,  $2.50. 

HUTCHINSON  (JONATHAN).  SYPHILIS.  In  one  pocket-size  12mo.  volume  of 
542  pages,  with  8  chromo-lithographic  plates.  Cloth,  $2. 25.  See  Series  of  Clinical  Man- 
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HYDE  (JAMES  NEVINS).  A  PRACTICAL  TREATISE  ON  DISEASES  OF 
THE  SKIN.  New  (4th )  edition,  thoroughly  revised.  In  one  octavo  volume  of  815  pages, 
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JACKSON  (GEORGE  THOMAS^.  THE  READY-REFERENCE  HANDBOOK 
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pages,  with  69  engravings,  and  one  colored  plate.  Cloth,  $2.75.  Just  ready. 

JAMIESON  (W.  ALLAN).  DISEASES  OF  THE  SKIN.  Third  edition.  In  one 
octavo  volume  of  656  pages,  with  1  engraving  and  9  double-page  chromo-lithographic 
plates.  Cloth,  $6. 

JEWETT  (CHARLES).    ELEMENTS  OF  OBSTETRICS.     In  one  12mo.  volume 

of  356  pages,  with  61  engravings  and  3  colored  plates.     Cloth,  $2.25.     Just  ready. 

JONES  (C.  HANDFIELD).  CLINICAL  OBSERVATIONS  ON  FUNCTIONAL 
NER  VO  US  DISORDERS.  Second  American  edition.  In  one  octavo  volume  of  340 
pages.  Cloth,  $3.25. 

JULER  (HENRY).  A  HANDBOOK  OF  OPHTHALMIC  SCIENCE  AND 
PRACTICE.  Second  edition.  In  one  octavo  volume  of  549  pages,  with  201  engrav- 
ings, 17  chromo-lithographic  plates,  test-types  of  Jaeger  and  Snellen,  and  Holmgren's 
Color-Blindness  Test.  Cloth,  $5.50;  leather,  $6.50. 

KIRK  (EDWARD  C.).  OPERATIVE  DENTISTRY.  See  American  Text-books  of 
Dentistry,  page  2. 

KING  (A.  F.  A.).  A  MANUAL  OF  OBSTETRICS.  Sixth  edition.  In  one  12mo. 
volume  of  532  pages,  with  221  illustrations.  Cloth,  $2.50. 

KLEIN  (E.).  ELEMENTS  OF  HISTOLOGY.  Fourth  edition.  In  one  pocket-size 
12mo.  volume  of  376  pages,  with  194  engravings.  Cloth,  $1.75.  See  Students'  Series  of 
Manuals,  page  14. 

LANDIS  (HENRY  G.).  THE  MANAGEMENT  OF  LABOR.  In  one  handsome 
12mo.  volume  of  329  pages,  with  28  illustrations.  Cloth,  $1.75. 

LA  ROCHE  (R.).  YELLOW  FEVER.  In  two  Svo.  volumes  of  1468  pages. 
Cloth,  $7. 

-  PNEUMONIA.     In  one  Svo.  volume  of  490  pages.     Cloth,  $3. 

LAURENCE  (J.  Z.1)  AND  MOON  (ROBERT  C.).  A  HANDY-BOOK  OF 
OPHTHALMIC  SURGERY.  Second  edition.  In  one  octavo  volume  of  227  pages, 
with  66  engravings.  Cloth,  $2.75. 

LAWSON  (GEORGE).    INJURIES  OF  THE  EYE,  ORBIT  AND  EYELIDS. 

From  the  last  English  edition.  In  one  handsome  octavo  volume  of  404  pages,  with  92 
engravings.  Cloth,  $3.50. 

LEA  (HENRY  C.).  CHAPTERS  FROM  THE  RELIGIOUS  HISTORY  OF 
SPAIN;  CENSORSHIP  OF  THE  PRESS;  MYSTICS  AND  ILLUMINATI; 
THE  ENDEMONIADAS ;  EL  SANTO  NINO  DE  LA  GUARDIA;  BRI- 
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A  HISTORY  OF  AURICULAR  CONFESSION  AND  INDULGENCES 

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FORMULARY  OF  THE  PAPAL  PENITENTIARY.     In  one  octavo  vol- 
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SUPERSTITION  AND  FORCE;  ESSAYS  ON  THE  WAGER  OF  LA  W, 

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LEA  (HENRY  C.).  STUDIES  IN  CHURCH  HISTORY.  The  Kise  of  the  Tem- 
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12mo.  volume  of  605  pages.  Cloth,  $2.50. 

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pages.     Cloth,  $4.50. 

LEE  (HENRY)  ON  SYPHILIS.     In  one  8vo.  volume  of  246  pages.     Cloth,  $2.25. 

LEHMANN  (C.  G.).  ^  MANUAL  OF  CHEMICAL  PHYSIOLOGY.  In  one 
8vo.  volume  of  327  pages,  with  41  engravings.  Cloth,  $2.25. 

LEISHMAN  (WILLIAM).  A  SYSTEM  OF  MIDWIFERY.  Including  the  Dis- 
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LOOMIS  (ALFRED  L.)  AND  THOMPSON  (W.  OILMAN),  Editors.  A  SYS- 
TEM OF  PR  A  CTICAL  MEDICINE.  In  Contributions  by  Various  American  Authors. 
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LUDLOW  (J.  L.).  A  MANUAL  OF  EXAMINATIONS  UPON  ANATOMY, 
PHYSIOLOGY,  SURGERY,  PRACTICE  OF  MEDICINE,  OBSTETRICS, 
MATERIA  MEDICA,  CHEMISTRY,  PHARMACY  AND  THERAPEUTICS. 
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of  816  pages,  with  370  engravings.  Cloth,  $3.25 ;  leather,  $3.75. 

LUFF  (ARTHUR  P.).  MANUAL  OF  CHEMISTRY,  for  the  use  of  Students  of 
Medicine.  In  one  12mo.  volume  of  522  pages,  with  36  engravings.  Cloth,  $2.  See 
Students'  Series  of  Manuals,  page  14. 

LYMAN  (HENRY  M.).  THE  PRACTICE  OF  MEDICINE  In  one  very  hand- 
some octavo  volume  of  925  pages  with  170  engravings.  Cloth,  $4.75;  leather,  $5.75. 

LYONS  (ROBERT  D.).  A  TREATISE  ON  FEVER.  In  one  octavo  volume  of  362 
pages.  Cloth,  $2.25. 

MACKENZIE  (JOHN  NOLAND).  THE  DISEASES  OF  THE  NOSE  AND 
THROAT.  In  one  handsome  octavo  volume  of  about  600  pages,  richly  illustrated. 
Preparing. 

MAISCH  (JOHN  M.).  A  MANUAL  OF  ORGANIC  MATERIA  MEDICA. 
New  (6th)  edition,  thoroughly  revised  by  H.  C.  C.  MAISCH,  Ph.G.,  Ph.D.  In  one  very 
handsome  12mo.  volume  of  509  pages,  with  285  engravings.  Cloth,  $3. 

MANUALS.  See  Students'  Quiz  Series,  page  14,  Students'  Series  of  Manuals,  page  14,  and 
Series  of  Clinical  Manuals,  page  13. 

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MAY   fC.  H.).    MANUAL  OF  THE  DISEASES  OF  WOMEN.     For  the  use  of 

Students  and  Practitioners.     Second  edition,  revised  by  L.  S.  RAU,  M.D.     In  one  12mo. 
volume  of  360  pages,  with  31  engravings.     Cloth,  $1.75. 

MITCHELL  (JOHN  K,).  REMOTE  CONSEQUENCES  OF  INJURIES  OF 
NERVES  AND  THEIR  TREATMENT.  In  one  handsome  12mo.  volume  of  239 
pages,  with  12  illustrations.  Cloth  $1.75.  Just  ready. 

MITCHELL  (S.  WEIR).  CLINICAL  LESSONS  ON  NERVOUS  DISEASES. 
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MORRIS    (HENRY).    SURGICAL    DISEASES  OF   THE   KIDNEY.     In  one 

12mo.  volume  of  554  pages,  with  40  engravings  and  6  colored  plates.     Cloth,  $2.25.     See 
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MORRIS  (MALCOLM).  DISEASES  OF  THE  SKIN.  In  one  square  8vo.  volume 
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MULLER  (J.).  PRINCIPLES  OF  PHYSICS  AND  METEOROLOGY.  In  one 
large  8vo.  volume  of  623  pages,  with  538  engravings.  Cloth,  $4.50. 

MUSSER  (JOHN  H.).  A  PRACTICAL  TREATISE  ON  MEDICAL  DIAG- 
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931  pages,  illustrated  with  177  engravings  and  11  full-page  colored  plates.  Cloth,  $5; 
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NATIONAL  DISPENSATORY.    See  SUM,  Maisch  &  Caspari,  page  14. 

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NATIONAL  MEDICAL  DICTIONARY.    See  Billings,  page  3. 

NETTLESHIP  (EJ.  DISEASES  OF  THE  EYE.  Fourth  American  from  fifth 
English  edition.  In  one  12mo.  volume  of  504  pages,  with  164  engravings,  test-types 
and  formulae  and  color-blindness  test.  Cloth,  $2. 

NORRIS  (WM.  F.)  AND  OLIVER  (CHAS.  AA  TEXT-BOOK  OF  OPHTHAL- 
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OWEN  (EDMUND).    SURGICAL  DISEASES  OF  CHILDREN.     In  one  12mo. 

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PARK  (ROSWELL),  Editor.  A  TREATISE  ON  SURGERY,  by  American  Authors. 
For  Students  and  Practitioners  of  Surgery  and  Medicine.  In  two  magnificent  octavo 
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PARRY  (JOHN  S.).  EXTRA-UTERINE  PREGNANCY,  ITS  CLINICAL 
HISTORY,  DIAGNOSIS,  PROGNOSIS  AND  TREATMENT.  In  one  octavo 
volume  of  272  pages.  Cloth,  $2.50. 

PARVIN  (THEOPHILUS).     THE  SCIENCE  AND  ART  OF  OBSTETRICS. 

Third  edition      In  one  handsome  octavo  volume  of  677  pages,  with  267  engravings  and 
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PAVY  (F.  WJ.  A  TREATISE  ON  THE  FUNCTION  OF  DIGESTION,  ITS 
DISORDERS  AND  THEIR  TREATMENT.  From  the  second  London  edition. 
In  one  8vo.  volume  of  238  pages.  Cloth,  $2. 

PAYNE   (JOSEPH  FRANK).    A   MANUAL  OF  GENERAL  PATHOLOGY. 

Designed  as  an  Introduction  to  the  Practice  of  Medicine.     In  one  octavo  volume  of  524 
pages,  with  153  engravings  and  1  colored  plate  /.     o 

PEPPER'S  SYSTEM  OF  MEDICINE.    See  page  2. 

PEPPER  (A.  J.).  SURGICAL  PATHOLOGY.  In  one  12mo  volume  of  511  pages, 
with  81  engravings.  Cloth,  $2.  See  Students'  Series  of  Manuals,  page  14. 

PICK  (T.  PICKERING).  FRACTURES  AND  DISLOCATIONS.  In  one  12mo. 
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PIRRIE  (WILLIAM).     THE  PRINCIPLES  AND  PRACTICE  OF  SURGERY. 

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PL  A  YF  AIR  (W.  S.).  A  TREATISE  ON  THE  SCIENCE  AND  PRACTICE 
OF  MID  WIFER  Y.  Sixth  American  from  the  eighth  English  edition.  Edited,  with 
additions,  by  R.  P.  HARRIS,  M.D  In  one  octavo  volume  of  697  pages,  with  217  engrav- 
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POLITZER  (ADAM).  A  TEXT-BOOK  OF  THE  DISEASES  OF  THE  EAR 
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Translated  by  OSCAR  DODD,  M.D ,  and  edited  by  SIR  WILLIAM  DALBY,  F.K.C.S.  In 
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POWER  (HENRY).  HUMAN  PHYSIOLOGY.  Second  edition.  In  one  12mo. 
volume  of  396  pages,  with  47  engravings.  Cloth,  $1.50.  See  Student's  Series  of  Manuals. 
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PURDY  (CHARLES  W.).  BRIGHT'S  DISEASE  AND  ALLIED  AFFEC- 
TIONS OF  THE  KIDNEY.  In  one  octavo  volume  of  288  pages,  with  18  engrav- 
ings. Cloth,  $2. 

PYE-SMITH  (PHILIP  H.).  DISEASES  OF  THE  SKIN.  In  one  12mo.  volume 
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QUIZ  SERIES.     See  Students'  Quiz  Series,  page  14. 

RALFE  (CHARLES  H.).  CLINICAL  CHEMISTRY.  In  one  12mo.  volume  of 
314  pages,  with  16  engravings.  Cloth,  $1.50.  See  Students'  Series  of  Manuals,  page  14. 

RAMSBOTHAM  (FRANCIS  HJ.  THE  PRINCIPLES  AND  PRACTICE  OF 
OBSTETRIC  MEDICINE  AND  SURGERY.  In  one  imperial  octavo  volume  of 
640  pages,  with  64  plates  and  numerous  engravings  in  the  text.  Strongly  bound  in 
leather,  $7. 

REICHERT   (EDWARD   T.).     A    TEXT-BOOK   ON  PHYSIOLOGY.     In  one 

handsome  octavo  volume  of  about  800  pages,  richly  illustrated.     Preparing. 

REMSEN   (IRA).     THE  PRINCIPLES  OF  THEORETICAL    CHEMISTRY. 

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REYNOLDS  (J.  RUSSELL).    A  SYSTEM  OF  MEDICINE.    Edited,  with  notes 
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RICHARDSON   (BENJAMIN  WARD).    PREVENTIVE  MEDICINE.    In  one 

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ROBERTS  (JOHN  B.).  THE  PRINCIPLES  AND  PRACTICE  OF  MODERN 
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-  THE  COMPEND  OF  ANATOMY.     For  use  in  the  Dissecting  Koom  and  in 
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ROBERTS  (SIR  WILLIAM).  A  PRACTICAL  TREATISE  ON  URINARJ 
AND  RENAL  DISEASES,  INCLUDING  URINARY  DEPOSITS.  Fourth 
American  from  the  fourth  London  edition.  In  one  very  handsome  8vo.  volume  of  609 
pages,  with  81  illustrations.  Cloth,  $3.50. 

ROBERTSON  (J.  McGREGOR).    PHYSIOLOGICAL  PHYSICS.    In  one  12mo. 

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ROSS  (JAMES).  A  HANDBOOK  OF  THE  DISEASES  OF  THE  NERVOUS 
SYSTEM.  In  one  handsome  octavo  volume  of  726  pages,  with  184  engravings.  Cloth, 
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SAVAGE  (GEORGE  H.).  INSANITY  AND  ALLIED  NEUROSES,  PRACTI- 
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551  pages,  with  18  typical  engravings.  Cloth,  $:>.  See  Series  of  Clinical  Manuals,  page  13. 

SCHAFER  (EDWARD  A.).  THE  ESSENTIALS  OF  HISTOLOGY,  DESCRIP- 
TIVE AND  PRACTICAL.  For  the  use  of  Students.  New  (4th)  edition.  In  one 
handsome  octavo  volume  of  311  pages,  with  325  illustrations.  Cloth,  $3 

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SCHREIBER  (JOSEPH).  A  MANUAL  OF  TREATMENT  BY  MASSAGE 
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SON,  M.D  ,  of  New  York.  In  one  handsome  octavo  volume  of  274  pages,  with  117  fine 
engravings. 

SENN  (NICHOLAS).  SURGICAL  BACTERIOLOGY.  Second  edition.  In  one 
octavo  volume  of  268  pages,  with  13  plates,  10  of  which  are  colored,  and  9  engravings. 
Cloth,  $2. 

SERIES  OF  CLINICAL  MANUALS.  A  Series  of  Authoritative  Monographs  on 
Important  Clinical  Subjects,  in  12mo.  volumes  of  about  550  pages,  well  illustrated.  The 
following  volumes  are  now  ready:  BROADBENT  on  the  Pulse,  $1.75;  YEO  on  Food  in 
Health  and  Disease,  new  (2d)  edition,  $2.50;  CARTER  and  FROST'S  Ophthalmic  Surgery, 
$2. 25 ;  HUTCHINSON  on  Syphilis,  $2. 25 ;  MARSH  on  Diseases  of  the  Joints,  $2 ;  MORRIS 
on  Surgical  Diseases  of  the  Kidney,  $2.25;  OWEN  on  Surgical  Diseases  of  Children,  $2; 
PICK  on  Fractures  and  Dislocations,  $2;  BUTLIN  on  the  Tongue,  $3.50;  SAVAGE  on 
Insanity  and  Allied  Neuroses,  $2 ;  and  TREVES  on  Intestinal  Obstruction,  $2. 
For  separate  notices,  see  under  various  authors'  names. 

SERIES  OF  STUDENTS'  MANUALS.    See  next  page. 

SIMON  (CHARLES  E.).  CLINICAL  DIAGNOSIS,  BY  MICROSCOPICAL 
AND  CHEMICAL  METHODS.  In  one  handsome  octavo  volume  of  504  pages,  with 
132  engravings  and  10  full-page  plates  in  colors  and  monochrome.  Cloth,  $3.50. 

SIMON  (W.).  MANUAL  OF  CHEMISTRY.  A  Guide  to  Lectures  and  Laboratory 
Work  for  Beginners  in  Chemistry.  A  Text-book  specially  adapted  for  Students  of  Phar- 
macy and  Medicine.  Fifth  edition.  In  one  8vo.  volume  of  501  pages,  with  44  engrav- 
ings and  8  plates  showing  colors  of  64  tests.  Cloth,  $3. 25- 

SLADE  (D.  D.).  DIPHTHERIA  ;  ITS  NATURE  AND  TREATMENT.  Second 
edition.  In  one  royal  12mo.  volume,  158  pages.  Cloth,  $1.25. 

SMITH  (EDWARD).     CONSUMPTION,-   ITS  EARLY  AND  REMEDIABLE 

STAGES.     In  one  8vo.  volume  of  253  pages.     Cloth,  $2.25. 

SMITH  (J.  LEWIS).  A  TREATISE  ON  THE  DISEASES  OF  INFANCY 
AND  CHILDHOOD.  New  (8th)  edition,  thoroughly  revised  and  rewritten  and 
greatly  enlarged.  In  one  large  8vo.  volume  of  983  pages,  with  273  illustrations  and 

4  full-page  plates.     Cloth,  $4.50  ;  leather,  $5.50. 

SMITH  (STEPHEN).  OPERATIVE  SURGERY.  Second  and  thoroughly  revised 
edition.  Jn  one  octavo  vol.  of  892  pages,  with  1005  engravings.  Cloth,  $4;  leather,  $5. 

SOLLY    (S.    EDWIN).     A    HANDBOOK   OF   MEDICAL    CLIMATOLOGY. 

Jn  one  handsome  octavo  volume  of  462  pages,  with  engravings  and  11  full-page  plates, 

5  of  which  are  in  colors.     Cloth,  $4.00.     Just  ready. 

STILLE  (ALFRED).  CHOLERA;  ITS  ORIGIN,  HISTORY,  CAUSATION, 
SYMPTOMS,  LESIONS,  PREVENTION  AND  TREATMENT.  Jn  one  12mo. 
volume  of  163  pages,  with  a  chart  showing  routes  of  previous  epidemics.  Cloth,  $1.25. 

THERAPEUTICS  AND  MA  TERIA  MEDIC  A.     Fourth  and  revised  edition 


In  two  octavo  volumes,  containing  1936  pages.     Cloth,  $10 ;  leather,  $12. 


Philadelphia,  706,  70S  and  710  Sansom  St.— New  York    111  Fifth  Ave.  (cor.  18th  St.) 


14  LEA    BROTHERS    &     CO.'S    PUBLICATIONS. 


STILLE    (ALFRED),   MAISCH   (JOHN    M.)   AND   CASPARI    (CHAS.   JR.). 

THE  NATIONAL  DISPENSATORY:  Containing  the  Natural  History,  Chemistry, 
Pharmacy,  Actions  and  Uses  of  Medicines,  including  those  recognized  in  the  latest  Phar- 
macopoeias of  the  United  States,  Great  Britian  and  Germany,  with  numerous  references 
to  the  French  Codex.  Fifth  edition,  revised  and  enlarged  in  accordance  with  and  em- 
bracing the  new  U.  S.  Phai-macopobia,  Seventh  Decennial  .Revision.  With  Supplement 
containing  the  new  edition  of  the  National  Formulary.  In  one  magnificent  imperial 
octavo  volume  of  2025  pages,  with  320  engravings  Cloth,  $7.25;  leather,  $8.  With 
ready  reference  Thumb-letter  Index.  Cloth,  $7.75;  leather,  $8.50. 

STIMSON  (LEWIS  A.).     A  MANUAL   OF  OPERATIVE  SURGERY.    New 

(3d)  edition.  In  one  royal  12mo.  volume  of  614  pages,  with  306  engravings.  Just  ready. 
Cloth,  $3.75. 

A  TREATISE  ON  FRACTURES  AND  DISLOCATIONS.  In  two  hand- 
some octavo  volumes.  Vol.  I.,  FRACTURES,  582  pages.  360  engravings.  Vol  11.,  DISLO- 
CATIONS, 540  pages,  163  engravings.  Complete  work,  cloth,  $5.50 ;  leather,  $7.50.  Either 
volume  separately,  cloth,  $3 ;  leather,  $4. 

STUDENTS'  QUIZ  SERIES.  A  New  Series  of  Manuals  in  question  and  answer  for 
Students  and  Practitioners,  covering  the  essentials  of  medical  science.  Thirteen  volumes, 
pocket  size,  convenient,  authoritative,  well  illustrated,  handsomely  bound  in  limp  cloth, 
and  issued  at  a  low  price.  1.  Anatomy  (double  number);  D.  Physiology;  3.  Chemistry 
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Nose;  11.  Obstetrics;  12.  Gynecology;  13.  Diseases  of  Children.  Price,  $1  each,  except 
Nos.  1  and  7,  Anatomy  and  Surgery,  which  being  double  numbers  are  priced  at  $1.75  each. 
Full  specimen  circular  on  application  to  publishers. 

STUDENTS'  SERIES  OF  MANUALS.  A  Series  of  Fifteen  Manuals  by  Eminent 
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$2;  BRUCE'S  Materia  Medica  and  Therapeutics  (fifth  edition),  $1.50;  TREVES'  Manual  of 
Surgery  (monographs  by  33  leading  surgeons),  3  volumes,  per  set,  $6 ;  BELL'S  Compara- 
tive Anatomy  and  Physiology,  $2;  ROBERTSON'S  Physiological  Physics,  $2;  GOULD'S 
Surgical  Diagnosis,  $2;  KLEIN'S  Elements  of  Histology  (4th  edition),  $1.75;  PEPPER'S 
Surgical  Pathology,  $2;  TREVES'  Surgical  Applied  Anatomy,  $2;  POWER'S  Human 
Physiology  (2d  edition',  $1.50;  EALFE'S  Clinical  Chemistry,  $1.50;  and  CLARKE  and 
LOCKWOOD'S  Dissector's  Manual,  $1.50 

For  separate  notices,  see  under  various  authors'  names. 

STURGES  (OCTAVIUS).  AN  INTRODUCTION  TO  THE  STUDY  OF  CLIN- 
ICAL MEDICINE.  1  n  one  ]2mo.  volume.  Cloth,  $1.25. 

SUTTON  (JOHN  BLAND).  SURGICAL  DISEASES  OF  THE  OVARIES 
AND  FALLOPIAN  TUBES.  Including  Abdominal  Pregnancy.  In  one  12mo.  vol- 
ume of  513  pages,  with  119  engravings  and  5  colored  plates.  Cloth,  $3. 

TUMORS,  INNOCENT  AND  MALIGNANT.     Their  Clinical  Features  and 

Appropriate  Treatment.  In  one  8vo.  volume  of  526  pages,  with  250  engravings  and 
9  full-page  plates.  Cloth,  $4.50. 

TAIT  (LAWSON).    DISEASES  OF  WOMEN  AND  ABDOMINAL  SURGERY. 

In  two  handsome  octavo  volumes.  Vol.  I.  contains  554  pages,  62  engravings,  and  3 
plates.  Cloth,  $3.  Vol.  II.,  preparing. 

TANNER  (THOMAS  HAWKES).  ON  THE  SIGNS  AND  DISEASES  OF 
PREGNANCY.  From  the  second  English  edition.  In  one  octavo  volume  of  490  pages, 
with  4  colored  plates  and  16  engravings.  Cloth,  $4.25. 

TAYLOR  (ALFRED  S.).  MEDICAL  JURISPRUDENCE.  New  American  from 
the  twelfth  English  edition,  specially  revised  by  CLARK  BELL,  ESQ.,  of  the  N.  Y.  Bar. 
In  one  octavo  vol.  of  about  800  pages,  with  about  75  engravings.  Cloth,  $4.50  ;  leather, 
$5.50.  Just  ready. 

Philadelphia   706,  708  and  710  Sansom  St  —  Hew  York,  III  Fifth  Ave.  (cor.  18th  St.). 


LEA    BROTHERS    &     CO:  S    PUBLICATIONS.  15 

TAYLOR  (ALFRED  S.).  ON  POISONS  IN  EELATION  TO  MEDICINE 
AND  MEDICAL  JURISPRUDENCE.  Third  American  from  the  third  London 
edition.  In  one  8vo.  volume  of  788  pages,  with  104  illustrations.  Cloth,  $5.50; 
leather,  $6.50. 

TAYLOR  (ROBERT  W.).  THE  PATHOLOGY  AND  TREATMENT  OF 
VENEREAL  DISEASES.  In  one  very  handsome  octavo  volume  of  1002  pages,  with 
230  engravings  and  7  colored  plates.  Cloth,  $5 ;  leather,  $6.  Net. 

A    CLINICAL    ATLAS    OF    VENEREAL    AND    SKIN    DISEASES. 


Including  Diagnosis,  Prognosis  and  Treatment.  In  eight  large  folio  parts,_  measuring 
14  x  18  inches,  and  comprising  213  beautiful  figures  on  58  full-page  chromo-lithographic 
plates,  85  fine  engravings,  and  425  pages  of  text.  Complete  work  now  ready.  Price  per 
part,  sewed  in  heavy  embossed  paper,  $2.50.  Bound  in  one  volume,  half  Eussia,  $27 ; 
half  Turkey  Morocco,  $28.  For  sale  by  subscription  only.  Address  the  publishers.  Spec- 
imen plates  by  mail  on  receipt  of  10  cents. 

A  PRACTICAL  TREATISE  ON  SEXUAL  DISORDERS  IN  THE  MALE 

AND  FEMALE.     In  one  octavo  volume  of  451  pages,  with  73  engravings  and  8  colored 
plates.     Cloth,  $3.     Net     Just  ready. 

TAYLOR  (SEYMOUR).  INDEX  OF  MEDICINE.  A  Manual  for  the  use  of  Senior 
Students  and  others.  In  one  large  12mo.  volume  of  802  pages.  Cloth,  $3  75. 

THOMAS  (T.  GAILLARD)  AND  MUNDE  (PAUL  P.).  A  PRACTICAL 
TREATISE  ON  THE  DISEASES  OF  WOMEN.  Sixth  edition,  thoroughly 
revised  by  PAUL  F.  MUNDE,  M.D.  In  one  large  and  handsome  tfctavo  volume  of  824 
pages,  with  347  engravings.  Cloth,  $5 ;  leather,  $6. 

THOMPSON  (SIR  HENRY).  CLINICAL  LECTURES  ON  DISEASES  OF 
THE  URINARY  ORGANS.  Second  and  revised  edition.  In  one  octavo  volume  of 
203  pages,  with  25  engravings.  Cloth,  $2.25. 

THE  PATHOLOGY  AND  TREATMENT  OF  STRICTURE  OF  THE 

URETHRA  AND   URINARY  FISTULA.     From  the  third  English  edition.     In 
one  octavo  volume  of  359  pages,  with  47  engravings  and  3  lithographic  plates.     Cloth, 
$3.50. 

TODD     (ROBERT    BENTLEY).       CLINICAL    LECTURES    ON    CERTAIN 

ACUTE  DISEASES.     In  one  8vo.  volume  of  320  pages.    Cloth,  $2.50. 

TREVES  (FREDERICK).  OPERATIVE  SURGERY.  In  two  8vo.  volumes  con- 
taining 1550  pages,  with  422  illustrations.  Cloth,  $9 ;  leather,  $11. 


—  A  SYSTEM  OF  SURGERY.  In  Contributions  by  Twenty-five  English  Sur- 
geons. In  two  large  octavo  volumes,  containing  2298  pages,  with  950  engravings  and 
4  full-page  plates.  Per  volume,  cloth,  $8. 


A  MANUAL  OF  SURGERY.     In  Treatises  by  33  leading  surgeons.     Three 

12mo.  volumes,  containing  1866  pages,  with  213  engravings.     Price  per  set,  $6.     See  Stu- 
dents' Series  of  Manuals,  page  14. 

THE  STUDENTS'   HANDBOOK  OF  SURGICAL  OPERATIONS.     In 

one  12mo.  volume  of  508  pages,  with  94  illustrations.     Cloth,  $2.50. 

-  SURGICAL  APPLIED  ANATOMY.     In  one  12mo.  volume  of  583  pages 
with  61  engravings.     Cloth,  $2.     See  Students'  Series  of  Manuals,  page  14. 

INTESTINAL  OBSTRUCTION.     In  one  12mo.  volume  of  522  pages,  with  60 


illustrations.     Cloth,  $2.     See  Series  of  Clinical  Manuals,  page  13. 

TUKE  (DANIEL  HACK).  THE  INFLUENCE  OF  THE  MIND  UPON  THE 
BODY  IN  HEALTH  AND  DISEASE.  Second  edition.  In  one  8vo.  volume  of 
467  pages,  with  2  colored  plates.  Cloth,  $3. 

VAUGHAN  (VICTOR  C.)  AND  NOVY  (FREDERICK  G.).  PTOMAINS, 
LEUCOMAINS,  TOXINS  AND  ANTITOXINS,  or  the  Chemical  Factors  in  the 
Causation  of  Disease.  New  (3d)  edition.  In  one  12mo.  volume  of  603  pages.  Cloth,  $3. 
Just  ready. 

Philadelphia,  706,  708  and  7/0  Sansom  St.— New  York,  III  Fifth  Ave.  (cor.  18th  St.). 


16  LEA    BROTHERS    &     CO.' S    PUBLICATIONS. 

VISITING  LIST.  THE  MEDICAL  NEWS  VISITING  LIST  for  1897.  Four 
styles:  Weekly  (dated  for  30  patients) ;  Monthly  (undated  for  120  patients  per  month) ; 
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each  week).  The  60-patient  book  consists  of  256  pages  of  assorted  blanks.  The  first 
three  styles  contain  32  pages  of  important  data,  thoroughly  revised,  and  160  pages  of 
assorted  blanks.  Each  in  one  volume,  price,  $1.25.  With  thumb-letter  index  for  quick 
use,  25  cents  extra  Special  rates  to  advance-paying  subscribers  to  THE  MEDICAL  NEWS 
or  THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES,  or  both.  See  page  1. 

WATSON  (THOMAS).  LECTURES  ON  THE  PRINCIPLES  AND  PRAC- 
TICE OF  PHYSIC.  A  new  American  from  the  fifth  and  enlarged  English  edition, 
with  additions  by  H.  HARTSHORNE,  M.D.  In  two  large  8vo.  volumes  of  1840  pages,  with 
190  engravings.  Cloth,  $9 ;  leather,  $11. 

WELLS  (J.  SOELBERG).  A  TREATISE  ON  THE  DISEASES  OF  THE 
EYE.  In  one  large  and  handsome  octavo  volume. 

WEST  (CHARLES).  LECTURES  ON  THE  DISEASES  PECULIAR  TO 
WOMEN.  Third  American  from  the  third  English  edition.  Jn  one  octavo  volume  of 
543  pages.  Cloth,  $3.75;  leather,  $4.75. 

ON  SOME  DISORDERS  OF  THE  NERVOUS  SYSTEM  IN  CHILD- 
HOOD.    In  one  small  12mo.  volume  of  127  pages.     Cloth,  $1. 

WHARTON  (HENRY  R.).  MINOR  SURGERY  AND  BANDAGING.  New  (3d) 
edition.  In  one  12mo  volume  of  594  pages,  with  475  engravings,  many  of  which  are 
photographic.  Cloth,  $3. 

WHITLA  (WILLIAM).  DICTIONARY  OF  TREATMENT,  OR  THERA- 
PEUTIC INDEX.  Including  Medical  and  Surgical  Therapeutics.  In  one  square 
octavo  volume  of  917  pages.  Cloth,  $4. 

WILSON  (ERASMUS).  A  SYSTEM  OF  HUMAN  ANATOMY.  A  new  and 
revised  American  from  the  last  English  edition.  Illustrated  with  397  engravings.  In 
one  octavo  volume  of  616  pages.  Cloth,  $4  ;  leather,  $5. 

—  THE  STUDENT'S  SO  OK  OF  CUTANEOUS  MEDICINE     In  one  12mo. 

volume.     Cloth,  $3  50. 

WINCKEL  ON  PATHOLOGY  AND  TREATMENT  OF  CHILDBED.  Trans- 
lated by  JAMES  R.  CHADWICK,  A.M.,  M.D.  With  additions  by  the  Author.  In  one 
octavo  volume  of  484  pages.  Cloth,  $4. 

WOHLER'S  OUTLINES  OF  ORGANIC  CHEMISTRY  Translated  from  the 
eighth  German  edition,  by  IRA  R  EM'S.  EN,  M.D.  In  one  12mo.  volume  of  550  pages. 
Cloth  $3. 

YEAR  BOOK  OF  TREATMENT  FOR  1897.  A  Critical  Review  for  Practitioners  of 
Medicine  and  Surgery.  In  contributions  by  24  well-known  medical  writers.  12mo.,  495 
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YEO  (I.  BURNEY).  FOOD  IN  HEALTH  AND  DISEASE.  New  (2d)  edition. 
In  one  12mo.  volume  of  592  pages,  with  4  engravings.  Cloth,  $2.50.  Just  ready.  See 
Series  of  Clinical  Manuals,  page  13. 

A  MANUAL  OF  MEDICAL  TREATMENT,  OR  CLINICAL  THERA- 
PEUTICS.   Two  volumes  containing  1275  pages.     Cloth,  $5.50. 

YOUNG  (JAMES  K.).  ORTHOPEDIC  SURGERY.  In  one  8vo.  volume  of  475 
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